russh is a Rust SSH client and server library that includes an SSH agent protocol implementation

Why it is Yellow

• CVSS 8.3 high

References

• https://github.com/Eugeny/russh/commit/3e04597dc54e36bfc85c21996f7d8d9d224e9826
• https://github.com/Eugeny/russh/commit/62db6e7defd6d244159da962ccccb029e785ce0f
• https://github.com/Eugeny/russh/releases/tag/v0.65.0
• https://github.com/Eugeny/russh/security/advisories/GHSA-vp5q-ff62-jwqv

Original description

russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. From 0.50.0-beta.12 until 0.65.0, the agent server's Connection::try_sign path in russh/src/keys/agent/server.rs recognizes SSH_AGENT_CONSTRAIN_CONFIRM but returns a hard-coded successful result instead of calling Agent::confirm. In applications that override Agent::confirm to require user approval or another policy check, a process that can reach the agent socket, including the remote side of a forwarded agent, can use a key added through ssh-add -c without that check and can authenticate or sign data as the user while the key remains loaded. The separate Agent::confirm_request hook still runs for every signing request, so checks implemented there remain effective, and implementations that retain the default always-successful Agent::confirm do not lose an approval check through this regression. This issue is fixed in version 0.65.0.