MISP Guard up to 1.3 Taxonomy Tag Validation input validation

Summaryinfo

A vulnerability was found in MISP Guard up to 1.3. It has been classified as problematic. Affected by this vulnerability is an unknown functionality of the component Taxonomy Tag Validation. This manipulation causes input validation. This vulnerability is tracked as CVE-2026-118173. The attack is possible to be carried out remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as problematic was found in MISP Guard up to 1.3. Affected by this vulnerability is an unknown code block of the component Taxonomy Tag Validation. The manipulation with an unknown input leads to a input validation vulnerability. The CWE definition for the vulnerability is CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. As an impact it is known to affect confidentiality. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-118173 since 10/27/2026. The exploitation appears to be easy. The attack can be launched remotely. Neither technical details nor an exploit are publicly available.

Upgrading to version 1.4 eliminates this vulnerability.

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Productinfo

Vendor

• MISP

Name

• Guard

Version

• 1.0
• 1.1
• 1.2
• 1.3

License

• open-source

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CPE 2.2info

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