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

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• 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.

From the GitHub advisory

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

Weakness type: CWE-288.

Product: github.com/l3montree-dev/devguard (Go) · Assigned by: GitHub_M · Published: 2026-05-12

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• 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.

Timeline

• 2026-05-05 — GitHub-reviewed advisory GHSA-2g9v-7mr5-fgjg published (critical)
• 2026-05-12 — CVE record published by GitHub_M
• 2026-05-13 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-2g9v-7mr5-fgjg github.com
2. CVE.org record CVE-2026-42300 cve.org
3. NVD entry CVE-2026-42300 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

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