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Vulnerability · Published Mar 23, 2026 · Assigned by GitHub_M

CVE-2026-33250Crash when receiving specially-crafted packets

High 7.5

In plain English

A high-severity improper input validation in freeciv21 from longturn. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 58% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.9%top 41.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Freeciv21 is a free open source, turn-based, empire-building strategy game. Versions prior to 3.1.1 crash with a stack overflow when receiving specially-crafted packets. A remote attacker can use this to take down any public server. A malicious server can use this to crash the game on the player's machine. Authentication is not needed and, by default, logs do not contain any useful information. All users should upgrade to Freeciv21 version 3.1.1. Running the server behind a firewall can help mitigate the issue for non-public servers. For local games, Freeciv21 restricts connections to the current user and is therefore not affected.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12freeciv3.0.6-1+deb12u1DSA-6173-1
Debian:12freeciv3.0.6-1+deb12u1DEBIAN-CVE-2026-33250
Debian:13freeciv3.1.4+ds-2+deb13u1DSA-6173-1
Debian:13freeciv3.1.4+ds-2+deb13u1DEBIAN-CVE-2026-33250
Debian:14freeciv3.2.4+ds-1DEBIAN-CVE-2026-33250
Ubuntu:25.10freecivno fix listedUBUNTU-CVE-2026-33250

Affected products (as reported)

VendorProductVersions
longturn freeciv21 < 3.1.1

Weakness: CWE-20, CWE-121 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References