Bug 2573422 (CVE-2026-128088)

Summary: CVE-2026-128088 russh: russh: SSH agent lock bypass via unverified state during confirmation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in russh. In the Secure Shell (SSH) agent implementation, a signature request made before the agent is locked can still be completed after the lock is engaged because the agent fails to revalidate its lock status following user confirmation. A connected peer or remote server using agent forwarding can initiate a signature request and obtain a valid cryptographic signature even while the agent is locked. This flaw allows an attacker to bypass agent lock protections and perform unauthorized signing operations, although private keys are not exposed.
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Description OSIDB Bzimport 2026-11-13 19:21:21 UTC 
russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. Prior to version 0.65.1, try_sign() captures an Arc<PrivateKey> before awaiting Agent::confirm() and does not revalidate the shared lock state or key presence after the await. This is a distinct residual defect in the remediation for CVE-2026-116794. A peer, including a remote SSH server using agent forwarding, can begin a confirmation-constrained signature request while the agent is unlocked and receive the signature after another connection locks the agent if the stale confirmation returns true. New post-lock requests are rejected and private key material is not disclosed, but the pending operation bypasses the current lock state. This issue is fixed in version 0.65.1.