Bug 2567863 (CVE-2026-111062)

Summary: CVE-2026-111062 russh: russh: Cryptographic restriction bypass via signature algorithm mismatch
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: low    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in russh. The SSH server fails to verify that the cryptographic signature algorithm in a public-key authentication payload matches the algorithm named in the authentication request. An authenticated remote client can exploit this flaw by claiming an approved algorithm while submitting a signature generated using a restricted or deprecated algorithm. This allows the client to bypass server cryptographic restrictions or cause the server to record misleading authentication audit logs.
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Description OSIDB Bzimport 2026-11-05 22:32:03 UTC 
russh is a Rust SSH client and server library. From version 0.34.0-beta.1 until version 0.64.0, its SSH server does not require the signature algorithm in a public-key authentication signature to match the algorithm named in the authentication request. A client possessing an authorized RSA private key can announce  rsa-sha2-512  while supplying a valid  ssh-rsa  SHA-1 signature, bypassing restrictions or producing misleading audit records when applications rely on the requested algorithm. A valid private-key signature remains required, and russh clients are not affected. This issue is fixed in version 0.64.0.