---
id: "CVE-2026-118173"
kind: "vulnerability"
aliases: ["CVE-2026-118173"]
title: "MISP Guard: incomplete tag check lets higher-classified data pass feed policy"
severity: "medium"
cvss: 6.1
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["misp", "misp-guard", "other", "self-hosted", "threat-intel", "tlp"]
not_affected_if: ["misp-guard-not-deployed", "no-required-taxonomy-configured"]
published_at: "2026-10-27T19:17:28+00:00"
first_seen_at: "2026-10-27T19:33:18+00:00"
updated_at: "2026-10-27T19:35:05+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-118173", "first_seen_at": "2026-10-27T19:33:18+00:00"}]
---

# MISP Guard: incomplete tag check lets higher-classified data pass feed policy

MISP Guard, a proxy that filters MISP feed data by taxonomy tags, only checked that one tag of a required taxonomy such as TLP was allowed, not every tag. An event or attribute carrying both an allowed tag like tlp:clear and a disallowed tag like tlp:red could be distributed to feed consumers that should only receive lower-classified data.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- unknown

## Fix

- unknown

## Timeline

- 2026-10-27T19:33:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-118173

## From the sources

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.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_