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Debian LTS firefox-esr Important Code Execution Risk DLA-4635-1

debian lts
Calendar Grey June 19, 2026
Dist Debian Esm H88
Discover critical security updates for Mozilla Firefox on Debian LTS addressing multiple code execution issues.
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...

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
important
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

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