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9.8

Firefox and Thunderbird DevTools can let attackers run code

CVE-2026-100810 · published 20 days ago
Summary

The developer tools built into Firefox and Thunderbird contain a flaw that could let a malicious web page execute code on a user’s machine. This affects the browsers and the associated JavaScript engines from Mozilla. Updating Firefox and Thunderbird to version 157 or newer resolves the issue.

What to do
  • Update mozilla firefox to version 157.0.0 or later.
  • Update mozilla thunderbird to version 157.0 or later.
Affected software
Ecosystem VendorProductAffected versions
– mozilla firefox < 157.0.0
– mozilla thunderbird < 157.0
Ubuntu:18.04:LTS canonical mozjs52 All versions
Ubuntu:18.04:LTS canonical mozjs38 All versions
Ubuntu:20.04:LTS canonical mozjs68 All versions
Ubuntu:22.04:LTS canonical mozjs102 All versions
Ubuntu:22.04:LTS canonical mozjs78 All versions
Ubuntu:22.04:LTS canonical mozjs91 All versions
Ubuntu:22.04:LTS canonical thunderbird All versions
Ubuntu:24.04:LTS canonical mozjs115 All versions
Original advisory text
Other issue in the DevTools component
Other issue in the DevTools component. This vulnerability was fixed in Thunderbird 157 and Firefox 157.
References
Fix within
Internet-facing 3 days
Internal 60 days
  • Not known to be exploited
  • Can be exploited automatically
  • Gives an attacker full control
Severity
9.8 Critical
Exploitation
<1% chance of attack within 30 days
Type
CWE-200Information Exposure
Timeline
Published29 Sep 2026
Updated19 Oct 2026
First seen29 Sep 2026
Sources
CVE-2026-100810 · NVD
CVE-2026-100810 · MITRE
UBUNTU-CVE-2026-100810 · OSV
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