CVE-2025-9866 — Protection Mechanism Failure in Google Chrome

CWE-693 — Protection Mechanism Failure8 documents8 sources
Severity
8.8HIGHNVD
EPSS
0.1%
top 81.35%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
3
Google ChromeChromiumPaloalto Prisma Browser
Timeline
PublishedSep 3
Latest updateOct 8

Description

Inappropriate implementation in Extensions in Google Chrome prior to 140.0.7339.80 allowed a remote attacker to bypass content security policy via a crafted HTML page. (Chromium security severity: Medium)

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HExploitability: 2.8 | Impact: 5.9

Affected Packages4 packages

▶CVEListV5google/chrome140.0.7339.80 — 140.0.7339.80
▶NVDgoogle/chrome< 140.0.7339.80
▶Debianchromium/chromium< 140.0.7339.80-1~deb12u1+2

🔴Vulnerability Details

2
OSV
CVE-2025-9866: Inappropriate implementation in Extensions in Google Chrome prior to 140↗2025-09-03
▶
CVEList
CVE-2025-9866: Inappropriate implementation in Extensions in Google Chrome prior to 140↗2025-09-03
▶

📋Vendor Advisories

4
Palo Alto
PAN-SA-2025-0016 Chromium: Monthly Vulnerability Update (October 2025)↗2025-10-08
▶
Microsoft
Chromium: CVE-2025-9866 Inappropriate implementation in Extensions↗2025-09-09
▶
Chrome
Stable Channel Update for Desktop: CVE-2025-9865↗2025-09-02
▶
Debian
CVE-2025-9866: chromium - Inappropriate implementation in Extensions in Google Chrome prior to 140.0.7339....↗2025
▶

🕵️Threat Intelligence

1
Bleepingcomputer
Microsoft September 2025 Patch Tuesday fixes 81 flaws, two zero-days↗2025-09-09
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CVE-2025-9866 — Protection Mechanism Failure in Google | cvebase