🛡️ CVE-2026-8949 — firefox

🟠 CVSS 7.5 — High ✅ No Known Exploit CWE-190 NVD
7.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Integer overflow in the Widget: Win32 component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, and Thunderbird 140.11.

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. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

CVE-2026-8949 is classified as CWE-190: Integer Overflow or Wraparound. Arithmetic produces a value too large for its type and wraps around, so a later size or bounds check passes when it should not.

Affected software

CVE-2026-8949 is recorded against 3 packages.

  • firefox (fixed in 151.0.0)
  • thunderbird (fixed in 151.0.0)
  • unknown

Timeline and source

Published on 19 May 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

bugzilla.mozilla.org
www.mozilla.org
www.mozilla.org
www.mozilla.org
www.mozilla.org

CVE-2026-8949 on other distributions

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

Details

Severity HIGH
CVSS Score 7.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE CWE-190
Public Exploit ✅ No
Source NVD
Published 2026-05-19
Updated 2026-08-11
Modified 2026-06-17
Fix URL N/A

Affected Packages

Software From version Fixed in
firefox — 151.0.0
thunderbird — 151.0.0
unknown — —

Similar Threats

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