vulnerability / NVI-00018262 / Revision 1
OpenClaude MCP OAuth Callback: State Check Bypass via error Param Leads to DoS
GitHub lists this reviewed advisory for @gitlawb/openclaude. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
6.5 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
@gitlawb/openclaude
source listed< 0.5.1
# OAuth State Validation Bypass via `error` Parameter Causes Local Server DoS in MCP Auth Callback --- ## Description 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. The vulnerable code looks like this: ```typescript if (!error && state !== oauthState) { rejectOnce(new Error('OAuth state mismatch - possible CSRF attack')) return } if (error) { cleanup() rejectOnce(new Error(errorMessage)) return } ``` When a request arrives with an `error` query parameter (e.g., `?error=anything`), the first condition becomes `false` because `!error` evaluates to `false`. This means the CSRF check is **never reached**. Execution falls through to the second block, where `cleanup()` is called — shutting down the local server and terminating the user's active authentication session. The attacker does not need to know the `state` value. Any re
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
Confirm current vendor support, compatibility and deployment evidence. This report has not tested a fix in your system. GitHub Advisory Database
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-c73c-x77g-854r ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
First indexed by Null; source disclosure date is shown separately.