Crash when receiving specially-crafted packets

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Summary

CVECVE-2026-33250
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-03-24 00:16:29 UTC
Updated2026-04-15 15:47:31 UTC
DescriptionFreeciv21 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.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from [email protected]

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

EPSS: 0.002290000 probability, percentile 0.457310000 (date 2026-04-15)

Problem Types: CWE-20 | CWE-121 | CWE-20 CWE-20: Improper Input Validation | CWE-121 CWE-121: Stack-based Buffer Overflow

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Longturn Freeciv21 affected < 3.1.1 Not specified

References

ReferenceSourceLinkTags
github.com/longturn/freeciv21/releases/tag/v3.1.1 [email protected] github.com
redmine.freeciv.org/issues/1955 [email protected] redmine.freeciv.org
github.com/longturn/freeciv21/commit/ad8e18ca22595529599782b2984bf44df8d... [email protected] github.com
github.com/longturn/freeciv21/security/advisories/GHSA-f76g-6w3f-f6r3 [email protected] github.com
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