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VulnerabilityPublished Updated

CVE-2026-13371: WatchGuard Fireware OS · Deserialization of Untrusted Data

Affects WatchGuard Fireware OSSource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium : upgrade to 2026.2.1 or 12.12.1 when convenient.

Data as of 14 Nov 2026, 20:44 UTC

CVSS 4.0 base score
6.9Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 48% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2026.2.1, 12.12.1, 12.11.9 +1
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 14 Nov 2026.

What to do

Upgrade Fireware to 2026.2.1 or 12.12.1 (OS); 12.11.9 (OS); 12.5.19 (OS).

Affected software

ProductAffectedFixed in
WatchGuardFireware OSAffected
  • >=2025.1 <2026.2.1
Fixed in
  • 2026.2.1
WatchGuardFireware OSAffected
  • >=12.0 <12.12.1
Fixed in
  • 12.12.1
WatchGuardFireware OSAffected
  • >=12.0 <12.11.9
Fixed in
  • 12.11.9
WatchGuardFireware OSAffected
  • >=12.0 <12.5.19
Fixed in
  • 12.5.19

AI-suggested

If you cannot patch yet, restrict administrator access to trusted personnel only and monitor for unusual activity related to the put_data endpoint. Avoid sending untrusted or malformed data to the management interface.

Description

An authenticated administrator can trigger a denial-of-service condition in the Fireware Management Web UI by sending malformed or crafted data to the put_data endpoint, which performs unsafe deserialization of the attacker-supplied input.

References

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