Chrome Zero-Day CVE-2025-6554 Under Active Attack — Google Issues Security Update

CVE-2025-2783 is a high-severity sandbox escape in Google Chrome on Windows, caused by an incorrect handle being provided in unspecified circumstances in Mojo, Chrome's inter-process communication layer. It is triggered remotely through a malicious file and requires user interaction; an attacker who has code running inside Chrome's sandboxed renderer can abuse the handle flaw to break out of the Windows sandbox and gain broader access to the host (CVSS scope change with high impact to confidentiality, integrity, and availability). All Google Chrome versions on Windows prior to 134.0.6998.177 are affected, per the vendor fix referenced by CISA. The flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2025-03-27, and related reporting links it to active exploitation in the ForumTroll APT's phishing campaign against Russian scholars using fake eLibrary emails; ransomware use is unknown. No public proof-of-concept is known, and EPSS assigns a 9.2% probability of exploitation within 30 days (95th percentile).

Do: Update Google Chrome on Windows to 134.0.6998.177 or later immediately and verify deployed browser versions across endpoints; the flaw is in the CISA KEV catalog, so federal agencies must apply vendor mitigations per BOD 22-01 timelines. Because exploitation is tied to malicious files delivered via phishing (e.g., the ForumTroll fake-eLibrary campaign), prioritize patching for users who open untrusted attachments and links, and hunt for associated phishing emails.

Insufficient policy enforcement in Loader in Google Chrome prior to 136.0.7103.113 allowed a remote attacker to leak cross-origin data via a crafted HTML page. (Chromium security severity: High)

CVE-2025-5419 is an out-of-bounds read and write (CWE-125, CWE-787) in the V8 JavaScript engine used by Google Chromium, rated High with a CVSS 3.1 score of 8.8. A remote attacker can trigger it by persuading a user to open a crafted HTML page (network attack vector, user interaction required, no privileges needed). Successful exploitation can corrupt the V8 heap, potentially giving the attacker code execution in the context of the browser with high impact on confidentiality, integrity, and availability. Anyone running the unpatched V8 engine is affected, including Google Chrome prior to 137.0.7151.68 and Chromium-based browsers such as Microsoft Edge that ship the vulnerable engine. The flaw is confirmed exploited in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2025-06-05, though ransomware use is not yet known.

Do: Update Google Chrome to 137.0.7151.68 or later and restart the browser to load the fixed V8 (verify the version at chrome://version); apply the corresponding Chromium 137-based security update for Microsoft Edge and confirm via edge://version. Federal agencies must apply vendor mitigations or follow BOD 22-01 cloud-service guidance per the KEV listing. Since exploitation occurs via attacker-crafted web pages, prompt patching is the primary mitigation, and no public PoC is currently known.

CVE-2025-6554 is a type confusion vulnerability (CWE-843) in the V8 JavaScript engine of Google Chrome, affecting versions prior to 138.0.7204.96. A remote attacker can trigger it by inducing a user to open a crafted HTML page, and the flaw permits arbitrary read and write within the browser renderer process. Successful exploitation yields high confidentiality and integrity impact, and V8 type confusion bugs are commonly used as the first stage toward a full browser compromise. Any user of an unpatched Chrome or Chromium-based browser is exposed, and the flaw is being actively exploited in the wild as a zero-day; CISA added it to the Known Exploited Vulnerabilities catalog on 2025-07-02. Ransomware usage is not confirmed (reported as unknown), and no public proof-of-concept is known.

Do: Update Chrome to 138.0.7204.96 or later (check chrome://settings/help) and restart the browser to load the patched V8; users of Chromium-derived browsers (Edge, Brave, Opera, etc.) should install their vendor's corresponding V8 patch. Organizations must apply vendor mitigations or follow BOD 22-01 guidance given the KEV listing, and should inventory managed browsers and force-update policies to confirm rollout.