🛡️ CVE-2026-8950 on Debian — firefox-esr

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Same-origin policy bypass in the Networking: HTTP component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

Distribution advisory

This page covers CVE-2026-8950 as tracked by Debian, for the package firefox-esr. The fix is available in version 140.11.0esr-1; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is changed, meaning a successful attack can affect components beyond the vulnerable one. Rated impact: confidentiality high, integrity high, availability none.

Weakness class

DEBIAN-CVE-2026-8950 is classified as CWE-346: Origin Validation Error. The origin of a message or request is not verified properly, so one source can pose as another.

Affected software

DEBIAN-CVE-2026-8950 is recorded against 2 packages.

  • firefox-esr (fixed in 140.11.0esr-1)
  • thunderbird (fixed in 1:140.11.0esr-1)

Timeline and source

Published on 19 May 2026 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2026-8950 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-05-19
Updated 2026-08-12
Modified 2026-08-04
Fix URL N/A

Affected Packages

Software From version Fixed in
firefox-esr — 140.11.0esr-1
thunderbird — 1:140.11.0esr-1

Similar Threats

Exploit Protection

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DEBIAN-CVE-2026-8950 carries CVSS 9.3 Critical rating. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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