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CVE-2026-42300 — Vulnerability in...

CRITICAL

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

Published May 5, 2026Updated May 20, 2026Source: osv

Summary

### 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

Advisory Timeline

  • First published May 5, 2026 (160 days ago).
  • Last revised May 20, 2026 — 15 days after initial publication.

Remediation

Upgrade to the fixed version using your package manager.

Go
Update github.com/l3montree-dev/devguard to 1.2.2 or later
go get github.com/l3montree-dev/devguard@v1.2.2

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (1)

Affects 1 ecosystem: go (1).

PackageEcosystemAffectedFixed In
github.com/l3montree-dev/devguard
go
All versions1.2.2

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 9.8 score means for each attack dimension.

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
—
Confidentiality
—
Integrity
—
Availability
—

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

References

Frequently Asked Questions

What is CVE-2026-42300?
DevGuard has an unauthenticated identity assertion via `X-Admin-Token` header This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 9.8/10).
How do I check if my project is affected by CVE-2026-42300?
CVE-2026-42300 affects github.com/l3montree-dev/devguard. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-42300 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score
9.8

Exploitation is straightforward and causes maximum impact. Patch immediately.

Also Known As

GHSA-2g9v-7mr5-fgjg
GO-2026-4988

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