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


- **Severity:** Medium 6.1 (`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`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 27 Oct 2026
- **Updated:** 27 Oct 2026
- **Also known as:** GHSA-v5vh-f252-qp24

## 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.

Weakness: CWE-285 (Improper Authorization), CWE-20 (Improper Input Validation)

## 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.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-118173 and fix it if it is affected.

What it is: CVE-2026-118173 is a medium-severity vulnerability in misp-guard, published on 27 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-118173 in the wild and no public exploit code.

Affected product: misp-guard. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-118173/ (Markdown: https://insights.sbomify.com/CVE-2026-118173/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-118173
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-118173
- OSV: https://osv.dev/vulnerability/CVE-2026-118173

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-118173/
Summaries are generated and may contain mistakes; the official description above is the record.