A heap-based buffer overflow flaw was found in Cyrus SASL

Why it is Yellow

• CVSS 7.5 high
• Remotely exploitable without logging in

References

• https://access.redhat.com/security/cve/CVE-2026-107161
• https://bugzilla.redhat.com/show_bug.cgi?id=2460420
• http://www.openwall.com/lists/oss-security/2026/10/09/20

Original description

A 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.