How severe is CVE-2026-42300?

No CVSS score has been assigned to CVE-2026-42300 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-42300?

CVE-2026-42300 affects the following packages: github.com/l3montree-dev/devguard (Go). Ecosystems affected: Go.

How do I fix CVE-2026-42300?

Update github.com/l3montree-dev/devguard to 1.2.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42300 is resolved across your whole dependency graph.

How do I detect CVE-2026-42300 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/l3montree-dev/devguard, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-42300 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-42300 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-42300 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-42300?

CVE-2026-42300 has an EPSS (Exploit Prediction Scoring System) score of 0.3%, placing it in the 17th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-42300?

CVE-2026-42300 is classified as CWE-288 (CWE-288). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-42300 published, and has it been updated?

CVE-2026-42300 was published on May 12, 2026 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-42300 — devguard

Fix: l3montree-dev/devguard@6f38310

CVE-2026-42300 is a CWE-288 vulnerability in github.com/l3montree-dev/devguard. A fix is available for github.com/l3montree-dev/devguard — see the affected versions and patch details below.

DevGuard: Unauthenticated identity assertion via `X-Admin-Token` header

Also known asGHSA-2g9v-7mr5-fgjgGO-2026-4988

Published

May 12, 2026

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-42300.

EPSS Exploitation Probability

via FIRST.org ↗

0.3%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs17th percentile — riskier than 17% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/l3montree-dev/devguard

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

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

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/l3montree-dev/devguard`	all versions	1.2.2`go get github.com/l3montree-dev/devguard@v1.2.2`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/l3montree-dev/devguard, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/l3montree-dev/devguard to 1.2.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-42300 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

### 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 reve

O3 Security · Impact-Aware SCA

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