Medium · CVSS 6.1CVE-2026-118173

MISP Guard Incomplete Tag Validation Allows Non-Allowed Taxonomy Tags to Bypass Feed Policy EnforcementCVE-2026-118173

Answer in brief

CVE-2026-118173 records a Medium severity (CVSS 6.1) vulnerability in MISP Guard Incomplete Tag Validation Allows Non-Allowed Taxonomy Tags to Bypass Feed Policy Enforcement. The current sources do not mark it as known exploited. The current feed maps MISP/misp-guard (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Oct 27, 2026Updated Oct 27, 2026Source checked Oct 27, 2026First seen by HOL Oct 27, 2026Material review Oct 27, 2026

Upstream Advisory

Key facts

Risk: Medium · CVSS 6.1
Exploitation: Not marked as known exploited
Affected software: 1 mapped package or product
Fix availability: Available

Why this deserves its current priority

CVSS is 6.1. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps MISP/misp-guard (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
MISP/misp-guardgeneric	>=0 <1.4	1.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for MISP/misp-guard.
Review the reported fix. Source-reported solution: The fix introduces a new validation function, check_required_taxonomy_tags_allowed, that iterates over every tag belonging to a required taxonomy and verifies each one is present in the configured allowed-tags list, raising a ForbiddenException if any tag is not allowed. This check is applied at both the event level and the attribute level. Additionally, an inherit_event_taxonomies flag is introduced so that attributes without their own required-taxonomy tags inherit the event's already-validated taxonomy, while attributes that do carry tags of the required taxonomy are still fully validated against the allowed list. This ensures that no non-allowed tag of a required taxonomy can pass the guard regardless of whether an allowed tag is also present.

Evidence timeline and material changes

Published upstream
Oct 27, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 27, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Oct 27, 2026

Sources and claim methodology

GitHub security advisorygithub.com

Upstream source 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.

Quoted source text, attributed separately from HOL analysis.

Package

Affected range

Fixed version

MISP/misp-guardgeneric

>=0 <1.4

1.4

Recommended response

Check inventory. Check lockfiles and deployed manifests for MISP/misp-guard.

Review the reported fix. Source-reported solution: The fix introduces a new validation function, check_required_taxonomy_tags_allowed, that iterates over every tag belonging to a required taxonomy and verifies each one is present in the configured allowed-tags list, raising a ForbiddenException if any tag is not allowed. This check is applied at both the event level and the attribute level. Additionally, an inherit_event_taxonomies flag is introduced so that attributes without their own required-taxonomy tags inherit the event's already-validated taxonomy, while attributes that do carry tags of the required taxonomy are still fully validated against the allowed list. This ensures that no non-allowed tag of a required taxonomy can pass the guard regardless of whether an allowed tag is also present.

Sources and claim methodology

Upstream source description

Quoted source text, attributed separately from HOL analysis.