---
title: "CVE-2026-42300: DevGuard has an unauthenticated identity assertion via `X-Admin-Token` header"
url: https://erroneo.us/security/cve/CVE-2026-42300/
description: "CVE-2026-42300 (github.com/l3montree-dev/devguard (Go)): DevGuard provides vulnerability management for the full software supply chain. Prior to 1.2.2, the…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-05-12
date_modified: 2026-05-13
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-42300"
kev: false
cvss: 9.3
epss: 0.00435
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-42300: DevGuard has an unauthenticated identity assertion via `X-Admin-Token` header

**Signal:** Critical and remotely reachable. No known exploitation yet, but it is network-reachable without credentials. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.4% , percentile 37: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 37% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes github.com/l3montree-dev/devguard (Go) < 1.2.2, fixed in 1.2.2 . Check your lockfile, including transitive dependencies.

## What it is

DevGuard provides vulnerability management for the full software supply chain. Prior to 1.2.2, the SessionMiddleware accepts a client-supplied X-Admin-Token HTTP request header and uses its raw string value as the authenticated userID when no Kratos session cookie is present. An unauthenticated attacker who knows or can guess a target user's Kratos identity UUID can issue requests as that user. Where the target user is an organisation admin or owner, this gives the attacker full control over that organisation's DevGuard resources. This vulnerability is fixed in 1.2.2.

## Affected packages

- Go `github.com/l3montree-dev/devguard` < 1.2.2 → fixed: 1.2.2

## Affected products (CVE record)

- l3montree-dev devguard: < 1.2.2

## Severity

- GitHub_M CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`
- GitHub CVSS 4.0: 9.3 `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none , automatable yes , technical impact total .
- FIRST EPSS (model of 2026-10-21): 0.43% probability of exploitation activity in the next 30 days; percentile 37.

## Sources

- [GitHub Advisory GHSA-2g9v-7mr5-fgjg](https://github.com/advisories/GHSA-2g9v-7mr5-fgjg)
- [CVE.org record CVE-2026-42300](https://www.cve.org/CVERecord?id=CVE-2026-42300)
- [NVD entry CVE-2026-42300](https://nvd.nist.gov/vuln/detail/CVE-2026-42300)
- [github.com](https://github.com/l3montree-dev/devguard/security/advisories/GHSA-2g9v-7mr5-fgjg)
- [github.com](https://github.com/l3montree-dev/devguard/commit/6f38310bf93b2a63df3055038f4da82b1f4e6d9a)

---
Source page: https://erroneo.us/security/cve/CVE-2026-42300/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt