What is CVE-2026-87491?
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)
The record classifies CVE-2026-87491 under weakness class CWE-787. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 64 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 8.8 — HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - EPSS (FIRST)
- 3.1% probability of exploitation in the next 30 days, higher than 87.4% of all scored CVEs
- CISA KEV
- Listed since 2026-09-09, federal remediation deadline 2026-09-23
- Threadlinqs priority
- 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
- Published
- 2026-09-09
Is CVE-2026-87491 being exploited?
CISA added CVE-2026-87491 to the Known Exploited Vulnerabilities catalog on 2026-09-09, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-09-23 under BOD 22-01. Weaponised exploit code for CVE-2026-87491 is publicly available. 2 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 75 in the Threadlinqs vulnerability feed.
Affected products and versions
- Google: Chrome
How to fix CVE-2026-87491
Vendor advisory: https://chromereleases.googleblog.com/2026/09/stable-channel-update-for-desktop_0808145027.html. Because CVE-2026-87491 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-09-23. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-87491
4 tracked threats in the Threadlinqs corpus reference CVE-2026-87491, either in the campaign’s CVE list or as an indicator on the campaign record.
- NCSC CTO Weekly Summary (week ending 2026-09-13): actively exploited Cisco FMC (CVE-2026-20079/20316), PaperCut NG/MF (CVE-2026-81578/82078), MikroTik RouterOS and FortiGate (CVE-2025-25249) flaws; NetScaler SAML bypass (CVE-2026-19490); BlueMoon exploit kit — CRITICAL · 2026-11-02
- September 2026 Major Cyber Attacks: ShinyHunters FBIJobs/PeopleSoft (CVE-2026-35273), Clop Leak Site Grav CMS Hijack (CVE-2026-42608), PaperCut AI-Agent Campaign, BlueMoon Zero-Day Chain, NetScaler C2 (CVE-2026-88771) — CRITICAL · 2026-10-27
- BlueMoon Exploit Kit Chains Chrome V8 Flaws CVE-2026-85046 and CVE-2026-87491 with Windows Kernel LPE CVE-2026-85880 — CRITICAL · 2026-10-10
- UTA0565 Chains Chrome and Windows Zero-Days (CVE-2026-85046, CVE-2026-87491, CVE-2026-85880) to Deploy CLEANGULP Malware — CRITICAL · 2026-09-27
Sources
Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories. This product uses the NVD API but is not endorsed or certified by the NVD.