# CVE-2026-94184: Fetchmail: fetchmail: stack-based buffer overflow in ntlm authentication (fetchmail-sa-2026-01)

Status: published. Published: 2026-09-21. Updated: 2026-11-06.

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.

## Remediation

- workaround: Rebuild fetchmail without --enable-NTLM (omit NTLM at configure time). Confirm with `fetchmail -V` that the build does not list +NTLM. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (fetchmail): ≥ 0:6.4.38-3.el10_2.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (fetchmail): ≥ 0:6.4.24-1.el8_10.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (fetchmail): ≥ 0:6.4.24-1.el9_8.1; < * (unaffected, rpm). Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (fetchmail): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (fetchmail): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 5.3 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L; source: CNA: redhat

- CVSS 3.1: 8.1 (high); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H; source: ADP: CISA-ADP

- CISA KEV: No listing in collected sources

- EPSS: 1.20% as of 2026-11-05; percentile 68.18%

- SSVC: exploitation none; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-121

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/errata/RHSA-2026:85959 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:86981 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/errata/RHSA-2026:86982 (CNA: redhat; vendor-advisory, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-94184 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2531984 (CNA: redhat)

- https://bugzilla.redhat.com/show_bug.cgi?id=2537395 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://gitlab.com/fetchmail/fetchmail/-/commit/cb5be5c38471eec19e519ace0bc569176317ea92 (CNA: redhat)

- https://www.fetchmail.info/fetchmail-SA-2026-01.txt (CNA: redhat)

- https://www.openwall.com/lists/oss-security/2026/06/27/8 (CNA: redhat)

- http://www.openwall.com/lists/oss-security/2026/09/23/1 (ADP: CVE)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-94184; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-94184; retrieved 2026-11-06; source updated Not reported

Revision: 5616e58745a66dc840f3e93f9bff32144f98904aca6e0e961b850d2189d06828

Canonical: https://y2.dev/cve/CVE-2026-94184

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