Description
A stack-based buffer overflow flaw was found in fetchmail when built with NTLM support. A malicious or compromised mail server advertising NTLM authentication can send a crafted Type 2 challenge that causes fetchmail to write past a fixed stack buffer while building the NTLM authenticate response. This may lead to remote code execution depending on stack-frame layout, or to authentication failure or process termination under memory hardening.
References10
- access.redhat.com/errata/RHSA-2026:85959
- access.redhat.com/errata/RHSA-2026:86981
- access.redhat.com/errata/RHSA-2026:86982
- access.redhat.com/security/cve/CVE-2026-94184
- bugzilla.redhat.com/show_bug.cgi?id=2531984
- bugzilla.redhat.com/show_bug.cgi?id=2537395
- gitlab.com/fetchmail/fetchmail/-/commit/cb5be5c38471eec19e519ac…
- www.fetchmail.info/fetchmail-SA-2026-01.txt
- www.openwall.com/lists/oss-security/2026/06/27/8
- www.openwall.com/lists/oss-security/2026/09/23/1
Metrics
- CVSS 3.1
-
5.3
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L - EPSS — exploit probability
- 1% percentile: 68 · as of 8 November 2026
- CWE
- CWE-121
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.