CVE-2026-107161

NameCVE-2026-107161
DescriptionA heap-based buffer overflow flaw was found in Cyrus SASL. The add_to_challenge() function in the DIGEST-MD5 plugin computes the size of the buffer needed for a challenge/response field before DIGEST-MD5 quoting is applied, but does not recompute that size when quoting (escaping special characters) makes the value longer. The under-sized buffer is then passed to strcat(), causing a heap-based out-of-bounds write whose size depends on attacker-controlled input. A malicious or on-path DIGEST-MD5 (or HTTP Digest) server can trigger this flaw in a connecting client by supplying a crafted challenge field, such as realm or nonce, most likely resulting in a crash of the client application.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
cyrus-sasl2 (PTS)bookworm2.1.28+dfsg-10vulnerable
trixie2.1.28+dfsg1-9vulnerable
forky, sid2.1.28+dfsg1-11vulnerable

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
cyrus-sasl2source(unstable)(unfixed)

Notes

https://github.com/cyrusimap/cyrus-sasl/issues/889
https://github.com/cyrusimap/cyrus-sasl/pull/892
https://bugzilla.redhat.com/show_bug.cgi?id=2460420

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