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8.6

Firefox Telemetry Component Allows Malicious Code Execution

CVE-2026-4687 · published 7 months ago
Summary

The Telemetry component in older versions of Firefox has a flaw that can allow malicious code to escape the security boundary. This means that if a user visits a malicious website, the website could potentially execute unauthorized code on their computer. Users of affected versions of Firefox should update to the latest version to prevent this issue.

What to do
  • Update debian firefox-esr to version 140.9.0esr-1~deb12u1.
  • Update debian firefox-esr to version 140.9.0esr-1~deb13u1.
  • Update debian firefox-esr to version 140.9.0esr-1~deb11u1.
  • Update debian firefox-esr to version 140.9.0esr-1.
  • Update debian thunderbird to version 1:140.9.0esr-1~deb11u1.
  • Update debian thunderbird to version 1:140.9.0esr-1~deb12u1.
  • Update debian thunderbird to version 1:140.9.0esr-1~deb13u1.
  • Update debian thunderbird to version 1:140.9.0esr-1.
Affected software
Ecosystem VendorProductAffected versions
– mozilla firefox < 115.34.0
< 149.0
>= 128.0, < 140.9.0
cpe:2.3:a:mozilla:firefox:*:*:*:*:esr:*:*:*
Debian:11 debian firefox-esr < 140.9.0esr-1~deb11u1
Fix: upgrade to 140.9.0esr-1~deb11u1
Debian:12 debian firefox-esr < 140.9.0esr-1~deb12u1
Fix: upgrade to 140.9.0esr-1~deb12u1
Debian:13 debian firefox-esr < 140.9.0esr-1~deb13u1
Fix: upgrade to 140.9.0esr-1~deb13u1
Debian:14 debian firefox-esr < 140.9.0esr-1
Fix: upgrade to 140.9.0esr-1
Debian:11 debian thunderbird < 1:140.9.0esr-1~deb11u1
Fix: upgrade to 1:140.9.0esr-1~deb11u1
Debian:12 debian thunderbird < 1:140.9.0esr-1~deb12u1
Fix: upgrade to 1:140.9.0esr-1~deb12u1
Debian:13 debian thunderbird < 1:140.9.0esr-1~deb13u1
Fix: upgrade to 1:140.9.0esr-1~deb13u1
Debian:14 debian thunderbird < 1:140.9.0esr-1
Fix: upgrade to 1:140.9.0esr-1
Original advisory text
Sandbox escape due to incorrect boundary conditions in the Telemetry component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird ...
Sandbox escape due to incorrect boundary conditions in the Telemetry component. This vulnerability was fixed in Firefox 149, Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
References
Fix within
Internet-facing 14 days
Internal At next upgrade
  • Not known to be exploited
  • Needs hands-on effort to exploit
  • Gives an attacker full control
Severity
8.6 High
Exploitation
<1% chance of attack within 30 days
Type
CWE-754Improper Check for Unusual or Exceptional Conditions
CWE-120Classic Buffer Overflow
CWE-501Trust Boundary Violation
Timeline
Published24 Mar 2026
Updated4 Nov 2026
First seen24 Mar 2026
Sources
CVE-2026-4687 · NVD
DEBIAN-CVE-2026-4687 · OSV
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