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Vulnerability record · CVE-2026-33250 · published 24 March 2026

CVE-2026-33250: Improper input validation vulnerability

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.

7.5 CVSS 3.1 High EPSS 1.2% · top 32.4% CWE-20 · Improper input validationCWE-121 · Stack-based buffer overflow Deferred
7.5CVSS 3.1 base score
1.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

LinkTags
https://github.com/longturn/freeciv21/commit/ad8e18ca22595529599782b2984bf44df8d69ed6
https://github.com/longturn/freeciv21/releases/tag/v3.1.1
https://github.com/longturn/freeciv21/security/advisories/GHSA-f76g-6w3f-f6r3
https://redmine.freeciv.org/issues/1955

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Source: NIST National Vulnerability Database (record CVE-2026-33250), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.