Vulnerability · Published Nov 4, 2026 · Assigned by VulnCheck

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

Medium 6.5

In plain English

A medium-severity stack buffer overflow in netrek-client-cow from quozl. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities).

Severity (CVSS 3.1)6.5Medium

Exploit odds (30 days)0.3%top 71.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Ubuntu:22.04:LTS	netrek-client-cow	no fix listed	UBUNTU-CVE-2026-121969
Ubuntu:24.04:LTS	netrek-client-cow	no fix listed	UBUNTU-CVE-2026-121969
Ubuntu:26.04:LTS	netrek-client-cow	no fix listed	UBUNTU-CVE-2026-121969
Ubuntu:26.10	netrek-client-cow	no fix listed	UBUNTU-CVE-2026-121969

Affected products (as reported)

Vendor	Product	Versions
quozl	netrek-client-cow	0 – through 3.3.3

Weakness: CWE-121 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

References

Patch Commit patch
https://github.com/quozl/netrek-client-cow product
https://github.com/quozl/netrek-client-cow/blob/3.3.3/short.c#L949 technical-description
https://github.com/quozl/netrek-client-cow/issues/11 issue-tracking
VulnCheck Advisory: netrek-client-cow through 3.3.3 Stack Buffer Overflow via handleSMessage third-party-advisory