CVE-2026-118173 MISP Guard Incomplete Tag Validation Allows Non-Allowed Taxonomy Tags to Bypass Feed Policy Enforcement
- Exploited in the wild
- Not known
- Fix
- None listed
What is CVE-2026-118173?
CVE-2026-118173 is a medium-severity vulnerability in misp-guard, published on 27 Oct 2026.
Official 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.
Which versions are affected by CVE-2026-118173?
How do I fix CVE-2026-118173?
No fix has been published for CVE-2026-118173 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-118173 being exploited?
There is no known exploitation of CVE-2026-118173 in the wild and no public exploit code.
Sources
Also known as GHSA-v5vh-f252-qp24.