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Fencer Vulns
high 7.5

CVE-2026-33250 json

Crash when receiving specially-crafted packets

published 2026-03-23 7 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-14642

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.9%
EPSS 0.9% chance of exploitation in 30 days, percentile 58%
public exploits
0
none known

Summary

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.

Patch / fix

  • freeciv Debian 12 3.0.6-1+deb12u1
  • freeciv Debian 13 3.1.4+ds-2+deb13u1
  • freeciv Debian 14 3.2.4+ds-1

debian advisories DEBIAN-CVE-2026-33250

  • freeciv Ubuntu Pro 16.04 LTS 2.5.3-1ubuntu0.1~esm1
  • freeciv Ubuntu Pro 18.04 LTS 2.5.10-1ubuntu0.1~esm1
  • freeciv Ubuntu Pro 20.04 LTS 2.6.2-1ubuntu0.1~esm1
  • freeciv Ubuntu Pro 22.04 LTS 2.6.6-1ubuntu0.1~esm1
  • freeciv Ubuntu Pro 24.04 LTS 3.1.0+ds-1ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2026-33250

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • freeciv openSUSE Leap 16.0 3.2.4-bp160.1.1
  • freeciv openSUSE Tumbleweed 3.2.4-1.1

opensuse advisories openSUSE-SU-2026:20423-1openSUSE-SU-2026:10401-1

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.85% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • longturn freeciv21

Classification

Weakness
  • CWE-20 Improper Input Validation
  • CWE-121 Stack-based Buffer Overflow

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.