CVE-2026-42073

OpenClaude's MCP OAuth Callback: State Check Bypass via error Param Leads to DoS

OpenClaude is an open-source coding-agent command line interface for cloud and local model providers. Prior to version 0.5.1, the OpenClaude MCP authentication flow starts a temporary local HTTP server to handle OAuth callbacks. To prevent CSRF attacks, the server validates a state parameter against an internally stored value. However, due to a logic flaw in the order of conditionals, an attacker can completely bypass this check and force the server to shut down — without knowing the state value at all. This issue has been patched in version 0.5.1.

Affected

Gitlawb · openclaude

CVSS v3.1 GITHUB

6.5 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

EPSS

0.29% chance of exploitation in the next 30 days, 20th percentile

Published

2026-06-02

Proof-of-concept exploits (1)

• advisories/GHSA-c73c-x77g-854r

Security advisories

• Gitlawb/openclaude/security/advisories/GHSA-c73c-x77g-854r
• Gitlawb/openclaude/commit/739b8d1f40fde0e401a5cbd2b9a55d88bd5124ad

References

• CVE Record
• NVD entry