Known exploited · Google
CVE-2026-87491: Google Chromium V8 Out of Bounds Write Vulnerability
What it is
Google Chromium V8 contains an out of bounds write vulnerability that allows a remote attacker to execute arbitrary code inside the sandbox via a crafted HTML page. This vulnerability could affect multiple web browsers that utilize Chromium, including, but not limited to, Google Chrome, Microsoft Edge, and Opera.
- Vendor
- Product
- Chromium V8
- Added to KEV
- September 9, 2026
- CISA due date
- September 23, 2026
- Ransomware use
- Unknown
- Weakness
- CWE-787: Out-of-bounds Write
What CISA requires
Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Forensic triage
No
What to do now
- Find every instance of Chromium V8 you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before September 23, 2026 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
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Train the engineers who fix it
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Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.