KEV Lag Tracker → CVE-2026-87491. Data verified against the official CISA KEV catalog and the National Vulnerability Database.
CISA added CVE-2026-87491 (Google Chromium V8) to the Known Exploited Vulnerabilities catalog on September 9, 2026. CISA listed it as actively exploited 0 days before its NVD publication date — exploitation was confirmed at or before public disclosure. A KEV listing is CISA’s official confirmation that a vulnerability is being exploited in the wild.
The Record
| CVE | CVE-2026-87491 |
| Vendor / product | Google Chromium V8 |
| Vulnerability | Google Chromium V8 Out of Bounds Write Vulnerability |
| CVSS base score | 8.8 |
| NVD publication date | September 9, 2026 |
| Added to CISA KEV | September 9, 2026 |
| Lag (public → KEV listing) | 0 days |
| Federal patch deadline | September 23, 2026 |
| Known ransomware use | No |
Measured against the 1720 entries in our tracker with verified publication dates, CVE-2026-87491 was flagged faster than 87% of them.
What CISA Reported
CISA describes the flaw as follows: “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.”
Federal Patch Deadline
Under Binding Operational Directive rules, U.S. federal agencies must remediate CVE-2026-87491 by September 23, 2026 — a 14-day remediation window from the KEV listing date. Private organizations are not bound by that deadline; CISA treats it as the benchmark for how urgently a confirmed-exploited flaw should be patched.
What EPSS Forecast Before the Confirmation
EPSS had no score for CVE-2026-87491 on the day before CISA confirmed exploitation. That normally means the CVE had not yet been published when it was already being exploited — a case no forecast could have flagged. Its current EPSS probability is 1.00%. See the EPSS accuracy analysis for how often this happens.
How This Compares to Google’s Track Record
At 0 days, CVE-2026-87491 was flagged faster than Google’s 7-day median across the 75 of its KEV entries with verified publication dates.
| Google in the CISA KEV catalog | Value |
|---|---|
| Tracked KEV entries | 75 |
| Median lag (public → KEV listing) | 7 days |
| 0-day rate (exploited at or before disclosure) | 24% |
| Entries tied to known ransomware campaigns | 0 |
Other Recent Google KEV Additions
| CVE | Product | Added to KEV | Lag (days) | Ransomware |
|---|---|---|---|---|
| CVE-2026-58704 | Pixel | September 16, 2026 | 1 | No |
| CVE-2026-85046 | Chromium V8 | September 4, 2026 | 1 | No |
| CVE-2026-11645 | Chromium V8 | June 9, 2026 | 0 | No |
| CVE-2026-5281 | Dawn | April 1, 2026 | 0 | No |
| CVE-2026-3909 | Skia | March 13, 2026 | 0 | No |
Defense guide: How to Detect Zero-day Vulnerability: Attack Chain & Defense — detection signals, attack chain and response steps for this class of attack.
Frequently Asked Questions
What is CVE-2026-87491?
CVE-2026-87491 is a vulnerability in Google Chromium V8 (Google Chromium V8 Out of Bounds Write Vulnerability) that CISA added to its Known Exploited Vulnerabilities catalog on September 9, 2026. A KEV listing is CISA’s official confirmation that the flaw is being exploited in the wild.
How long was CVE-2026-87491 public before CISA confirmed exploitation?
0 days before its NVD publication date — CISA listed it as exploited at or before the vulnerability was formally published, which is the signature of a zero-day.
What is the federal patch deadline for CVE-2026-87491?
U.S. federal agencies must remediate CVE-2026-87491 by September 23, 2026, a 14-day window from the KEV listing date. Private organizations are not bound by that deadline, but CISA treats it as the benchmark for how urgently a confirmed-exploited flaw should be patched.
Is CVE-2026-87491 used in ransomware campaigns?
CISA has not flagged CVE-2026-87491 as known to be used in ransomware campaigns. That field reflects confirmed campaign use, not the absence of risk.
How does this compare to other Google vulnerabilities?
Across 75 Google entries with verified publication dates, the median lag is 7 days and 24% were exploited at or before disclosure. CVE-2026-87491, at 0 days, is faster than that median.
Related Coverage
- Google’s CVE-2026-85046 Was Exploited in 1 Days — Faster Than Its 7-Day Median (September 2026)
- Google’s CVE-2026-58704 Was Exploited in 1 Days — Faster Than Its 7-Day Median (September 2026)
Primary Sources
- CISA Known Exploited Vulnerabilities Catalog — the official listing that confirms active exploitation, and the source of the KEV date on this page.
- NVD — CVE-2026-87491 — publication date, CVSS score and the full technical record.
- Vendor advisory — chromereleases.googleblog.com — Google’s own disclosure, with the affected versions and the fix.
How We Track This
This page is generated from our CISA KEV Lag Tracker, which syncs the official CISA KEV catalog daily and records the date each CVE is added. For every entry we retrieve the original NVD publication date and compute the lag in calendar days. No date or figure on this page is estimated or taken from a third-party source — they come directly from CISA and NVD records. Free to cite with attribution to CVEDaily (CC BY 4.0).