Google Chrome users have faced a one-two punch of critical “zero-day” vulnerabilities in recent weeks. In the past two weeks (late June to early July 2025), Google scrambled to patch at least one major Chrome security flaw that attackers were actively exploiting before a fix was available - the very definition of a zero-day. In this blog-style report, we'll break down each critical Chrome zero-day uncovered or patched in this period, explaining what the vulnerabilities are (with CVE identifiers), who found them, how they were exploited, and why they matter. We'll also provide an easy-to-follow timeline of discovery and disclosure for each issue, and, most importantly, what you should do to stay safe. The tone here is both journalistic and user-friendly - no dense jargon, just the facts and analysis you need.
What Happened? A Quick Overview of Recent Chrome Zero-Days
In late June 2025, Google's Chrome browser was hit with a serious security bug that was under active attack by malicious actors. This prompted Google to issue an emergency update to Chrome's stable version on all platforms bleepingcomputer.commalwarebytes.com. This vulnerability, now tracked as CVE-2025-6554, turned out to be the fourth Chrome zero-day exploit revealed in 2025 bleepingcomputer.com. For context, earlier in the year Chrome had already seen three other zero-day flaws (in March, May, and June), including one used in high-profile espionage campaigns bleepingcomputer.com. The flurry of patches underscores how determined attackers are at finding cracks in the world's most popular web browser - and how fast Google is moving to plug them.
Before we dive into the details of each flaw, let's clarify zero-day: it means attackers discovered the vulnerability before a patch was available, giving victims zero days to fix it. These are the kinds of bugs hackers love - they can silently compromise systems until the vendor rushes out a fix. Chrome's recent zero-days have been particularly severe, allowing attackers to potentially execute arbitrary code on your device just by getting you to visit a malicious website malwarebytes.commalwarebytes.com. In other words, simply browsing could infect you if your browser isn't up to date. Below we summarize each critical Chrome zero-day from the past two weeks, including what it is, how it was found, and what was done about it.
CVE-2025-6554 - Type Confusion in V8 (Late June 2025)
CVE-2025-6554 is a high-severity type confusion vulnerability in Chrome's V8 JavaScript engine, and it was being actively exploited in the wild in late June 2025 chromereleases.googleblog.combleepingcomputer.com. This flaw is essentially an error in Chrome's memory handling. In technical terms, Chrome prior to version 138.0.7204.96 was susceptible to a type confusion bug in V8, which “allowed a remote attacker to perform arbitrary read/write [operations] via a crafted HTML page” nvd.nist.gov. In plain language, an attacker could craft a malicious website such that when you visited it, the bug would misidentify data types in the JavaScript engine. This confusion would let the attacker manipulate memory in unexpected ways, possibly causing Chrome to execute the attacker's code or crash bleepingcomputer.commalwarebytes.com. It's the kind of vulnerability that can lead directly to spyware installation or other malware delivery with no warning to the user.
Discovery and Timeline: This zero-day was discovered by Clément Lecigne of Google's Threat Analysis Group (TAG), a team that specializes in hunting sophisticated, state-sponsored threats. He reported the bug to Google on June 25, 2025 chromereleases.googleblog.com. Google's response was remarkably swift - within 24 hours (by June 26), they deployed a server-side configuration change to mitigate the issue for Chrome users on the Stable channel chromereleases.googleblog.combleepingcomputer.com. This behind-the-scenes tweak helped reduce harm even before a full browser update was ready. By the end of June, Google had prepared an emergency client update: on June 30, 2025, a Stable Channel Update for Chrome Desktop was released, bumping the version to 138.0.7204.96 (and .97) on Windows (and .92/.93 on macOS, .96 on Linux) which contains the complete fix bleepingcomputer.commalwarebytes.com. In effect, Chrome's developers went from discovery to global patch in roughly five days - a testament to the severity of the bug and the urgency to protect users.
Who Found It: Clément Lecigne is a well-known researcher on Google's TAG team. TAG often detects exploits being used by government-backed hackers or commercial spyware vendors. The fact that TAG itself discovered CVE-2025-6554 “signals it may have been weaponized in highly targeted attacks possibly involving nation-state actors or surveillance operations” thehackernews.com. Indeed, Google publicly acknowledged awareness that “an exploit for CVE-2025-6554 exists in the wild” chromereleases.googleblog.com, meaning hackers were already using it to attack unsuspecting users. Google hasn't published details on who exactly was exploiting this flaw (and likely won't until most users have updated bleepingcomputer.com), but TAG's involvement hints at a sophisticated adversary. In past cases, such browser zero-days have been used against high-profile targets like journalists, dissidents, or IT administrators - people whose browsers are gateways to sensitive data.
Affected Versions: According to the official NVD entry and Google's advisory, any Chrome version before 138.0.7204.96 (on Linux and Windows) and before 138.0.7204.92 on Mac was vulnerable nvd.nist.govmalwarebytes.com. Chrome for Android was likewise patched in version 138.0.7204.63 for Android (which includes the same fixes as desktop) chromereleases.googleblog.com. Essentially, if you had not updated Chrome by the end of June 2025, your browser was at risk. This flaw is considered “High” severity (it earned an 8.1 CVSS score in CISA's assessment nvd.nist.gov), and given its active exploitation, it warranted immediate patching.
Why It's Significant: CVE-2025-6554 is significant both technically and practically. Technically, type confusions on the V8 engine can often be escalated to full arbitrary code execution, effectively letting an attacker run malware on your system just by visiting a booby-trapped web page malwarebytes.commalwarebytes.com. Practically, this means a user could get compromised with no action beyond loading a website - no downloads or clicks required. This particular bug's active exploitation suggests it was not just theoretical. Though Google withheld specifics, the Threat Analysis Group's involvement implies the vulnerability was being used in real-world attacks, possibly to deploy spyware or other malicious payloads on targeted users thehackernews.commalwarebytes.com. For instance, previous Chrome zero-days have been used in tandem with other exploits to escape the browser sandbox and install malware on the underlying OS. While we don't yet know if CVE-2025-6554 was paired with a sandbox escape, Google did note it was the fourth Chrome zero-day of the year and part of a disturbing pattern bleepingcomputer.com. (For reference, in March 2025, a Chrome sandbox escape flaw CVE-2025-2783 was used in espionage attacks targeting Russian media and government entities bleepingcomputer.com.) All this underlines that CVE-2025-6554 wasn't an isolated glitch - it was a weapon being actively aimed at users, making Google's quick fix critical.
CVE-2025-5419 - Out-of-Bounds Read/Write in V8 (June 2025)
Just a few weeks before the CVE-2025-6554 saga, Chrome had faced another serious zero-day known as CVE-2025-5419. This was an “out-of-bounds read and write” memory vulnerability in Chrome's V8 engine - again in the core component that executes JavaScript and WebAssembly chromereleases.googleblog.comnvd.nist.gov. In simpler terms, CVE-2025-5419 was a memory corruption bug: Chrome could be tricked into reading or writing data outside the bounds of what it should, potentially leading to heap corruption and giving attackers a path to run arbitrary code nvd.nist.gov. Like CVE-2025-6554, this bug could likely be exploited via a malicious HTML or JavaScript snippet on a webpage to make Chrome misbehave in dangerous ways.
Discovery and Timeline: CVE-2025-5419 was discovered in late May 2025 by Clément Lecigne and Benoît Sevens, both from Google's Threat Analysis Group chromereleases.googleblog.com. They reported the vulnerability on May 27, 2025 chromereleases.googleblog.com. Google treated this with equal urgency: the very next day (May 28), a configuration change was pushed to the Chrome Stable channel to mitigate the issue until a permanent patch was readychromereleases.googleblog.com. Shortly thereafter, on June 2, 2025, Google released an out-of-band Stable Channel Update to version 137.0.7151.68/.69 for Windows and Mac (137.0.7151.68 for Linux) which contained the full fix chromereleases.googleblog.comchromereleases.googleblog.com. This rapid turnaround (about one week from report to patch release) shows how severe the bug was considered. Google also publicly announced on June 3 that an exploit for this flaw had been spotted in the wild, making it the second Chrome zero-day of 2025 at that point thehackernews.com.
Who Found It: The discovery credit goes to Google's TAG team researchers Clément Lecigne and Benoît Sevens chromereleases.googleblog.com. This is notable because TAG typically hunts for signs of active exploitation by sophisticated threat actors. Indeed, Google confirmed “Google is aware that an exploit for CVE-2025-5419 exists in the wild” chromereleases.googleblog.com. No public attribution was given about which hackers or groups were using this exploit. However, given TAG's involvement, we can infer the attacks were likely targeted. For example, earlier in 2025 the first Chrome zero-day (CVE-2025-2783 in March) was caught by Kaspersky researchers as part of a spy operation targeting Russian organizations thehackernews.com. Similarly, CVE-2025-5419 might have been used in nation-state espionage or by criminals against high-value Chrome users. By mid-2025, CVE-2025-5419 was added to the U.S. CISA's Known Exploited Vulnerabilities catalog with a directive for organizations to patch it by late June threatprotect.qualys.comnvd.nist.gov - strong evidence that authorities viewed it as a clear and present danger.
Affected Versions: Any Chrome version prior to 137.0.7151.68 (the fixed build) was vulnerable to CVE-2025-5419 nvd.nist.gov. This includes Chrome on all major desktop platforms. The emergency patch released on June 2 brought Chrome to v137.0.7151.68 (or .69 on certain systems) which closed the hole chromereleases.googleblog.comthreatprotect.qualys.com. Microsoft, whose Edge browser is based on Chromium, also released a corresponding Edge Stable update (v137.0.3296.62) to fix the same underlying issue threatprotect.qualys.com, highlighting that the vulnerability extended to all Chromium-based browsers. The vulnerability was rated High severity (CVSS 8.8) by Google and security analysts thehackernews.comthehackernews.com. Out-of-bounds write flaws are particularly serious because they can often be transformed into powerful exploits to achieve code execution or to break out of browser sandboxes when combined with other bugs.
Exploitation and Significance: Like the later CVE-2025-6554, this CVE-2025-5419 was being actively exploitedbefore the patch - making it a true zero-day. Google's advisory refrained from giving details about the attacks, as is customary, in order to prevent copycat exploitation thehackernews.com. What we do know is that by the time Google announced the fix, this was the second Chrome zero-day of 2025 known to be used in attacks thehackernews.com. (The next ones would be CVE-2025-4664 in May - which was patched but not clearly seen in attacks - and then CVE-2025-6554 in June). In practice, an out-of-bounds read/write in the V8 engine could allow an attacker who exploits it to corrupt the browser's memory heap and potentially execute arbitrary code within Chrome's process nvd.nist.gov. Usually, Chrome's sandbox would limit the damage to the browser itself; however, even code execution in Chrome can lead to credential theft, spyware installation, or cross-process exploits to escalate privileges. The significance of CVE-2025-5419 is underscored by how quickly Google reacted and by external warnings - CISA urging patching and security firms releasing alerts to “Update Chrome Today!” reddit.comhelpnetsecurity.com. It demonstrated once again that motivated adversaries are constantly scrutinizing Chrome's code for any memory safety slip-ups they can use. The fact that this was yet another V8 engine bug also highlights that browser scripting engines remain a prime target for attackers, given their complexity and deep access to system resources through JIT compilers, etc.
A Broader Trend: Chrome Zero-Days and Why They Keep Appearing
The two vulnerabilities above (CVE-2025-5419 in early June and CVE-2025-6554 in late June) came back-to-back, putting Chrome users at heightened risk. They weren't isolated incidents - they form part of a broader trend of recurring Chrome zero-day exploits in recent years. By July 2025, Chrome had already seen four zero-day patches in the first half of the year bleepingcomputer.com. For comparison, Google Chrome had 10 zero-day vulnerabilities patched in all of 2024 bleepingcomputer.com, indicating that 2025 was on track to be another heavy year for emergency Chrome updates.
Why is this happening? Part of the reason is simply Chrome's popularity and wide usage. Attackers, whether financially motivated cybercriminals or state-sponsored espionage groups, will invest time in finding fresh Chrome exploits because a successful Chrome zero-day can potentially give them access to millions of targets. Chrome's security team is actually very proactive - many of these flaws are caught by Google's own researchers or by external researchers who promptly report them. For instance, CVE-2025-4664 (patched in May 2025) was reported and fixed before there was evidence of broad malicious use; it was a high-severity issue that could “allow attackers to hijack accounts” if chained correctly bleepingcomputer.com. Google often patches such issues preemptively, which is why not every severe bug becomes a full-blown incident. However, the ones that slip through (like 2783, 5419, 6554) show that determined hackers can still occasionally get one step ahead, even if only for a short time.
Another trend is who is finding and using these zero-days. We see Google's Threat Analysis Group playing a big role in detection, which implies many of these exploits are being used in targeted attacks (often politically motivated). For example, the CVE-2025-2783 sandbox escape in March 2025 was discovered after it was used to plant malware on Russian media and government networks bleepingcomputer.com - likely a nation-state operation. The TAG team's involvement in June's bugs suggests similar high-level threat actors (they explicitly focus on spyware and state-backed hacking malwarebytes.com). In short, Chrome zero-days are valuable cyber weapons, and multiple adversaries (from spy agencies to exploit brokers) are searching for them or buying them. Google, in turn, has ramped up mitigations (like the quick config pushes) and layered defenses (Chrome's sandbox, Site Isolation, frequent auto-updates) to make exploitation harder.
It's also worth noting that while Chrome's architecture has many security features, its complexity (especially engines like V8 and components like Blink) means bugs will inevitably emerge. Memory safety issues like type confusions and out-of-bounds writes are particularly common vectors - hence Google's investments in technologies like Chromium's MiraclePtr and ongoing efforts to use memory-safe languages for new code. But until those efforts bear fruit, users must remain vigilant and promptly update when patches arrive.
How to Stay Safe - Security Recommendations for Chrome Users
The good news is that defending against these Chrome vulnerabilities is straightforward for most users: update your browser. Google Chrome is designed to update itself automatically, but here are some clear steps and tips to ensure you're protected:
Check Your Chrome Version and Update Manually if Needed: Open Chrome's menu (the three-dot icon in the top-right), go to Help > About Google Chrome. This will display your current version and automatically trigger Chrome to check for updates thehackernews.com. The latest patched versions (as of early July 2025) are 138.0.7204.96 or higher on Windows/Linux, and 138.0.7204.92 or higher on Mac malwarebytes.com. If your version is lower, Chrome should start downloading the update. Apply the update by relaunching Chrome when prompted malwarebytes.com. Note: Simply leaving Chrome open won't update it - a restart is required to complete the patch installation malwarebytes.com.
Enable and Monitor Automatic Updates: Chrome's auto-update is usually on by default. However, if you never restart your browser, updates can be pending indefinitely malwarebytes.com. Make it a habit to fully close and reopen Chrome periodically so it can apply updates. In organizational settings, IT admins should ensure policies aren't blocking auto-updates. Consider using Google's management policies or endpoint management solutions to force updates after a release. For businesses, enabling automatic patch management and monitoring browser version compliance is critical thehackernews.com to ensure all machines get the fix, especially when zero-days are involved.
Update Other Chromium-Based Browsers: If you use alternatives like Microsoft Edge, Brave, Opera, or Vivaldi, update them as well. These browsers share the Chromium engine, meaning they were likely vulnerable to the same underlying issues until they picked up Chrome's patches. Microsoft and others typically release their own updates quickly in such cases threatprotect.qualys.com. Check the browser's help->about page for updates. Google's advisory explicitly urges users of Chromium-based browsers to apply available fixes thehackernews.com.
Stay Informed on Security Alerts: It's wise to keep an eye on official channels like Chrome Releases Blog for announcements of emergency updates, or enable Chrome's browser to automatically update. Additionally, follow trusted cybersecurity news sites (such as The Hacker News, BleepingComputer, etc.) which often report on Chrome zero-day patches as soon as they're out. Being aware that a patch is available can prompt you to verify your browser is updated properly.
Practice Safe Browsing Habits (But Don't Rely Only On Them): While zero-days can sometimes strike via any website (including legitimate sites compromised by hackers), you can reduce risk by avoiding clicking unknown or suspicious links, especially those sent via email or messaging. Many Chrome exploits are used in targeted attacks via spear-phishing - for example, a link promising a hot news video could actually hide an exploit page. Use Chrome's built-in Safe Browsing feature (enabled by default) which can warn about known malicious sites. However, no browsing caution can replace patching, because determined attackers can sometimes even hide exploits in ads on legitimate sites. So, consider safe browsing habits as an extra layer on top of keeping Chrome updated.
Leverage Security Tools: Ensure you have reputable antivirus or anti-malware software on your system, which might catch or block some exploitation attempts. While these tools can't guarantee protection against an unknown browser exploit, they can sometimes detect suspicious behavior or payloads dropped by the exploit. Browser extensions like script blockers or security add-ons (for example, Malwarebytes' Browser Guard or Microsoft Defender SmartScreen in Edge) could provide additional warnings or block known exploit kits malwarebytes.com. Again, these are supplementary defenses - staying current with patches is the primary solution.
In summary, the key recommendation is simple: update Chrome (or any browser you use) as soon as a security fix is released, especially for zero-days. Google has made it easy with automatic updates, but user vigilance is still required to ensure those updates apply. With the CVE-2025-6554 and CVE-2025-5419 incidents, those who updated Chrome in time were protected from the ongoing attacks. Those who delayed remained at risk. As of July 2025, if your Chrome is up-to-date (check the “About Chrome” page for version 138.0.7204.96/97 or later malwarebytes.com), you are safeguarded against these two particular threats.
References and Further Reading
For those interested in the nitty-gritty details or official statements, we've compiled some authoritative sources:
Google Chrome Releases Blog - Official Advisories: Google's announcements for the Stable Channel updates that fixed these flaws are available on their blog. See the posts from June 2, 2025 (for CVE-2025-5419) and June 30, 2025 (for CVE-2025-6554) chromereleases.googleblog.comchromereleases.googleblog.com. These confirm the CVEs, credit the finders, and note that exploits were in the wild.
NIST National Vulnerability Database (NVD) Entries: The NVD entries for CVE-2025-5419 and CVE-2025-6554 provide technical descriptions and track the official patch versions nvd.nist.govnvd.nist.gov. They also show when these were added to the CISA Known Exploited Vulnerabilities catalog nvd.nist.govnvd.nist.gov.
Security News Coverage: Articles from reputed cybersecurity news sites offer more human-readable analysis. Notably, BleepingComputer's piece “Google fixes fourth actively exploited Chrome zero-day of 2025” (July 1, 2025) summarizes the CVE-2025-6554 update and provides context on earlier zero-days bleepingcomputer.combleepingcomputer.com. The Hacker News also ran stories: e.g., “Chrome Zero-Day CVE-2025-6554 Under Active Attack Google Issues Security Update” thehackernews.comthehackernews.comand “New Chrome Zero-Day Actively Exploited; Google Issues Emergency Out-of-Band Patch” (about CVE-2025-5419) thehackernews.comthehackernews.com. These articles are useful for understanding the impact and advice in layman's terms.
Security Bulletins and Blogs: Several security companies posted alerts about these vulnerabilities. For instance, Malwarebytes Labs urged users to update Chrome immediately and explained the nature of the CVE-2025-6554 bug in an accessible way malwarebytes.commalwarebytes.com. Qualys ThreatProtect provided a detailed brief on CVE-2025-5419, including version info and mitigation steps threatprotect.qualys.comthreatprotect.qualys.com. These can be good additional reads for IT professionals managing multiple machines.
Keeping browsers secure is an ongoing battle, but awareness and prompt action make a huge difference. Chrome's recent zero-days demonstrate that while attackers are constantly probing for weaknesses, the combination of vigilant security teams and attentive users can minimize the window of opportunity for bad actors. Stay updated, stay informed, and you'll significantly reduce your exposure to these cutting-edge threats.
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