# CVE-2026-121969: netrek-client-cow through 3.3.3 Stack Buffer Overflow via handleSMessage

Status: published. Published: 2026-11-04. Updated: 2026-11-04.

netrek-client-cow through 3.3.3 contains a stack-based buffer overflow vulnerability in handleSMessage() in short.c that allows malicious servers to overflow a 100-byte stack buffer by sending oversized SP_S_MESSAGE packets. A malicious Netrek server or man-in-the-middle on the plaintext TCP connection can send overlong or unterminated message bodies to write server-controlled bytes onto the stack and crash the client.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/quozl/netrek-client-cow/commit/fb322e74abee3b0b76a9c5a31df6aab5585d3127

## Affected products and versions

- quozl / netrek-client-cow: ≥ 0; ≤ 3.3.3 (affected, custom). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 7.1 (high); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-121

## Exploit evidence

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

## References

- https://github.com/quozl/netrek-client-cow/commit/fb322e74abee3b0b76a9c5a31df6aab5585d3127 (CNA: VulnCheck; patch)

- https://github.com/quozl/netrek-client-cow (CNA: VulnCheck; product)

- https://github.com/quozl/netrek-client-cow/blob/3.3.3/short.c#L949 (CNA: VulnCheck; technical-description)

- https://github.com/quozl/netrek-client-cow/issues/11 (CNA: VulnCheck; issue-tracking)

- https://www.vulncheck.com/advisories/netrek-client-cow-through-3.3.3-stack-buffer-overflow-via-handlesmessage (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121969; retrieved 2026-11-04; source updated 2026-11-04

Revision: 0bcbd958abde4f8a382a9b6d18f041514cb3973decbe9893746eb9f11c646579

Canonical: https://y2.dev/cve/CVE-2026-121969

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