Rmcp: OAuth client SSRF filter checks host strings, not resolved addresses
Affects rmcpSource GCVE Database
Rated High by Threat Radar's AI analysis
- Patch
- Available – fixed in 3.7.0
Data as of 9 Nov 2026, 11:35 UTC
What to do
Upgrade rmcp to 3.7.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
crates.iormcppkg:cargo/rmcpOther threats | Affected
| Fixed in
|
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AI-suggested
A fix is available in rmcp version 3.7.0, which adds DNS resolution and address policy enforcement for all resolved addresses and redirects. Deployments that use hostnames resolving to private addresses for their authorization servers should use the provided method AuthorizationManager::new_allowing_private_addresses. Clients using custom HTTP clients via new_with_oauth_http_client must implement their own outbound address policies to prevent SSRF. Users should upgrade to version 3.7.0 or later to remediate this vulnerability.
Description
The rmcp OAuth client versions from 2.0.0 up to but not including 3.7.0 have a server-side request forgery (SSRF) vulnerability. The client only inspected host strings to decide if it should fetch authorization server metadata, failing to resolve hostnames to their IP addresses. This allowed malicious servers to cause the client to send requests to internal IP addresses, potentially reaching unauthenticated internal HTTP services. The issue was fixed in version 3.7.0 by adding DNS resolution and address policy checks on all resolved addresses and redirects.