Bug 2562400 (CVE-2026-116773)

Summary: CVE-2026-116773 russh: russh: Denial of Service via unbounded memory allocation in extension handling
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in russh. An unbounded memory allocation issue allows a malicious Secure Shell (SSH) server to cause a Denial of Service (DoS) on connecting clients. By repeatedly sending crafted pre-authentication extension packets, the server forces the client to store an unlimited number of extension entries without clearing or deduplicating them. This behavior leads to progressive memory exhaustion and can crash the client process.
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Description OSIDB Bzimport 2026-10-27 20:33:08 UTC 
russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. Prior to 0.65.0, the client Session::process_packet path in russh/src/client/encrypted.rs accepts repeated packets encoded with russh's private msg::EXT_INFO = 7 before authentication, while the standards-compliant EXT_INFO message number 82 does not reach the affected handler. The handle_ext_info function appends every parsed extension name to received_extensions without clearing, deduplicating, or bounding the vector. A malicious SSH server that deliberately sends private message number 7 can therefore retain an unbounded number of attacker-controlled extension names for the session lifetime, causing progressive client memory exhaustion. This issue is fixed in version 0.65.0.