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Debian LTS DLA-4635-1 Firefox ESR Critical Code Execution Threats

debian lts
Calendar Grey June 19, 2026
Dist Debian Esm H88
Multiple security issues fixed in Firefox ESR for Debian, addressing code execution, privilege escalation, and more.
Multiple security issues have been found in the Mozilla Firefox web browser, which could potentially result in the execution of arbitrary code, bypass of the same-origin policy, pr...
Topics%20covered

Topics Covered

security advisory critical arbitrary code execution information disclosure firefox-esr deblts

Summary

For Debian 11 bullseye, these problems have been fixed in version
140.12.0esr-1~deb11u1.

For Debian 12 bookworm, these problems have been fixed in version
140.12.0esr-1~deb12u1.

We recommend that you upgrade your firefox-esr packages.

For the detailed security status of firefox-esr please refer to
its security tracker page at:
https://security-tracker.debian.org/tracker/firefox-esr

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://wiki.debian.org/LTS


Severity
critical
Lowest
Low
Medium
High
Critical

Package: firefox-esr
Version: 140.12.0esr-1~deb11u1 140.12.0esr-1~deb12u1
CVE ID: CVE-2026-12289 CVE-2026-12290 CVE-2026-12291 CVE-2026-12292

Topics%20covered

Topics Covered

security advisory critical arbitrary code execution information disclosure firefox-esr deblts

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