What is CVE-2026-87433?

CVE-2026-87433 is a high-severity vulnerability in Google Chrome, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 8.8/10. Published 2026-09-09.

How severe is CVE-2026-87433?

High severity. CVSS v3 base score is 8.8 out of 10.

Vulnerability in Google Chrome

CVE-2026-87433

Race condition in FileAPI in Google Chrome prior to 153.0.8010.36 allowed a remote attacker who had compromised the renderer process to bypass site isolation via a crafted HTML page. (Chromium security severity: Medium)

Vulnerability class: TOCTOU (Time-of-Check to Time-of-Use)

Published 2026-09-09 · last modified 2026-09-10.

CVSS v3 metric

CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.003 (19.2th percentile), scored 2026-10-24.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 19th percentile — 19.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000

Affected products

Google Chrome

Weakness classification (CWE)

CWE-367 — Time-of-check Time-of-use (TOCTOU) Race Condition

References

chromereleases.googleblog.com/2026/09/stable-channel-update-for-desktop_0808145… (Release Notes, Vendor Advisory)
issues.chromium.org/issues/497574154 (Permissions Required)

Frequently asked questions

What is CVE-2026-87433?: CVE-2026-87433 is a high-severity vulnerability in Google Chrome, classified under Time-of-check Time-of-use (TOCTOU) Race Condition. CVSS score: 8.8/10. Published 2026-09-09.
How severe is CVE-2026-87433?: High severity. CVSS v3 base score is 8.8 out of 10.