CVE-2026-116794: russh: Agent server never calls `Agent::confirm`, so keys added with the confirm constraint (`ssh-add -c`) sign without confirmation
The agent server in russh::keys::agent::server never calls Agent::confirm before signing with a key that was added with the confirm constraint. That constraint is SSH_AGENT_CONSTRAIN_CONFIRM (RFC 9987 §5.2.7.2), which is what ssh-add -c sends.
The call was replaced by a hard-coded true in 3e04597 (“Native async traits encore”, #455), first released in 0.50.0-beta.12. Every release since, up to and including 0.64.1, signs requests for confirm-constrained keys without asking the Agent implementation. A user who added a key with -c is therefore never asked to confirm.
References
- github.com/Eugeny/russh/commit/3e04597dc54e36bfc85c21996f7d8d9d224e9826
- github.com/Eugeny/russh/commit/62db6e7defd6d244159da962ccccb029e785ce0f
- github.com/Eugeny/russh/releases/tag/v0.65.0
- github.com/Eugeny/russh/security/advisories/GHSA-vp5q-ff62-jwqv
- github.com/advisories/GHSA-vp5q-ff62-jwqv
- nvd.nist.gov/vuln/detail/CVE-2026-116794
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