What’s Vulnerable › Vulnerabilities

CVE-2026-116773: russh's SSH client is susceptible to unbounded allocations via EXT_INFO packets

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-27 · updated 2026-10-30
• Weakness: CWE-770

Description

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.

Affected products

• Eugeny russh: before 0.65.0

References

• https://github.com/Eugeny/russh/commit/b33e93beec393e6d29eee69c1b8831736724ee75
• https://github.com/Eugeny/russh/releases/tag/v0.65.0
• https://github.com/Eugeny/russh/security/advisories/GHSA-4p9f-7p9m-5vfg
• https://github.com/Eugeny/russh/security/advisories/GHSA-4p9f-7p9m-5vfg

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