A firefox-esr security update has been released for Debian GNU/Linux 11 and 12 to address a buffer overflow.

[SECURITY] [DSA 5509-1] firefox-esr security update

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Debian Security Advisory DSA-5509-1 security@debian.org
https://www.debian.org/security/ Moritz Muehlenhoff
September 29, 2023 https://www.debian.org/security/faq
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Package : firefox-esr
CVE ID : CVE-2023-5217

A buffer overflow in VP8 media stream processing has been found in the
Mozilla Firefox web browser, which could potentially result in the
execution of arbitrary code.

For the oldstable distribution (bullseye), this problem has been fixed
in version 115.3.1esr-1~deb11u1.

For the stable distribution (bookworm), this problem will be fixed
via the libvpx source package, Firefox ESR in Bookworm links dynamically
against libvpx.

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 Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://www.debian.org/security/