DevGuard has an unauthenticated identity assertion via X-Admin-Token header

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

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 · score source

EPSS

• CVE-2026-42300: 0.26% estimated exploitation activity in the next 30 days; percentile 17.42 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact 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. Patches The release v1.2.2 patches this issue. Update your DevGuard API Instances to this version. Workarounds Configure a reverse proxy to strip the X-Admin-Token header before sending requests to the DevGuard API. Resources Fixed commit: https://github.com/l3montree-dev/devguard/commit/6f38310bf93b2a63df3055038f4da82b1f4e6d9a

Published by the source

5 May 2026, 20:58 UTC

Last modified by the source

13 May 2026, 16:26 UTC

Source last checked

26 Oct 2026, 15:20 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-2g9v-7mr5-fgjg

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# Patch Next advisory brief: CVE-2026-42300

Advisory: DevGuard has an unauthenticated identity assertion via `X-Admin-Token` header
IDs: CVE-2026-42300, GHSA-2g9v-7mr5-fgjg
Record: https://patchnext.com/advisories/cve-2026-42300 (revision 1, source checked 26 Oct 2026, 15:20 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/l3montree-dev/devguard 1.2.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/l3montree-dev/devguard: affected < 1.2.2; fixed in 1.2.2

## Suggested inspection (read-only)
- Go github.com/l3montree-dev/devguard: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/l3montree-dev/devguard.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-2g9v-7mr5-fgjg (GitHub-reviewed advisory GHSA-2g9v-7mr5-fgjg lists affected ranges: Go github.com/l3montree-dev/devguard >=0 <1.2.2)

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