Home / mailings [SECURITY] [DSA 6584-1] varnish security update
Posted on 25 October 2026
Debian Security Advisory- -------------------------------------------------------------------------
Debian Security Advisory DSA-6584-1 security@debian.org
https://www.debian.org/security/ Aron Xu
October 25, 2026 https://www.debian.org/security/faq
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Package : varnish
CVE ID : CVE-2026-34475 CVE-2026-93894
Several vulnerabilities were discovered in Varnish Cache, an HTTP
accelerator, which could result in cache poisoning, authentication bypass
or denial of service.
CVE-2026-34475
Tom Kinnaird discovered a deficiency in the parsing of HTTP/1.1
absolute-form request targets. If the request URL is passed unchecked
to a backend which accepts absolute-form URIs, a remote attacker
could potentially poison the cache or bypass authentication. The
issue affects requests for root URLs.
CVE-2026-93894
Tristan Madani discovered a workspace buffer overflow in the .upper()
and .lower() string methods of the Varnish Configuration Language.
A remote attacker with knowledge of the active configuration could
craft a request which exhausts the remaining workspace during case
conversion, causing the worker process to crash and restart,
resulting in denial of service. Exploitation depends on the
configuration using these methods on attacker-controlled strings
and on the applicable request size limits.
For the stable distribution (trixie), these problems have been fixed in
version 7.7.0-3+deb13u2.
We recommend that you upgrade your varnish packages.
For the detailed security status of varnish please refer to
its security tracker page at:
https://security-tracker.debian.org/tracker/varnish
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/
Mailing list: debian-security-announce@lists.debian.org
