---
title: "CVE-2026-87491: Google Chromium V8 Out of Bounds Write Vulnerability"
url: https://erroneo.us/security/cve/CVE-2026-87491/
description: "CVE-2026-87491 (Google Chromium V8): Exploited in the wild (CISA KEV). Out of bounds write in V8 in Google Chrome prior to 153.0.8010.36 allowed a remote…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-09-09
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-87491"
kev: true
cvss: 8.8
epss: 0.03142
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-87491: Google Chromium V8 Out of Bounds Write Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Google Chromium V8. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-09-09, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-09-23 ; treat that as the outer limit, not the target.
- EPSS 3.1% , percentile 88: FIRST’s model estimates a 3.1% chance of exploitation activity in the next 30 days, higher than 88% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
- Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.
- Editorial verdict: Check exposure. Chrome V8 Zero-Days CVE-2026-85046 and CVE-2026-87491 — Both were exploited zero-days, but Chrome and Edge fixed them in early September and auto-update has had six weeks to deliver the fix; the job now is finding browsers that did not update, not a scramble.

## What it is

Out of bounds write in V8 in Google Chrome prior to 153.0.8010.36 allowed a remote attacker to execute arbitrary code inside the sandbox via a crafted HTML page. (Chromium security severity: Medium)

## Affected products (CVE record)

- Google Chrome: 153.0.8010.36 < 153.0.8010.36

## Severity

- CISA-ADP CVSS 3.1: 8.8 `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`

## Exploitation

- CISA KEV: added 2026-09-09; federal due date 2026-09-23. Known ransomware use: Unknown.
- CISA required action: 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.
- CISA SSVC assessment: exploitation active , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 3.14% probability of exploitation activity in the next 30 days; percentile 88.

## Sources

- [Listed in CISA KEV notes (chromereleases.googleblog.com)](https://chromereleases.googleblog.com/2026/09/stable-channel-update-for-desktop_0808145027.html)
- [CVE.org record CVE-2026-87491](https://www.cve.org/CVERecord?id=CVE-2026-87491)
- [NVD entry CVE-2026-87491](https://nvd.nist.gov/vuln/detail/CVE-2026-87491)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-87491)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk)
- [Listed in CISA KEV notes (cisa.gov)](https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk)
- [issues.chromium.org](https://issues.chromium.org/issues/543557673)

---
Source page: https://erroneo.us/security/cve/CVE-2026-87491/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt