russh's SSH client is susceptible to unbounded allocations via EXT_INFO packets

russh · Allocation without limits · CWE-770

Affectedrussh

FixNo fix listed yet.

PublishedOct 27, 20:23 · GitHub_M

ScoredOct 27 · 4.3 · GitHub_M

Exploit code publicNone known · checked 21:18 UTC

ExploitedNone known · CISA KEV checked 22:08 UTC

What we know

No known exploitation. CISA KEV, checked 22:08 UTC.

No public exploit code known. Exploit-DB, Metasploit, Nuclei, checked 21:18 UTC.

An attacker only needs network access to the target. No login needed. CVSS: network, no privileges.

Someone has to open, click or run something first. CVSS: user interaction required.

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.

From GitHub_M

Affected and fixed versions

ProductAffectedFixed inrussh< 0.65.0–

Exploit code

Exploit-DBnone knownMetasploitnone knownNucleinone known

References

github.com/Eugeny/russh/security/advisories/GHSA-4p9f-7p9m-5vfg · github.comrefsource_CONFIRM github.com/Eugeny/russh/commit/b33e93beec393e6d29eee69c1b8831736724ee75 · github.comrefsource_MISC github.com/Eugeny/russh/releases/tag/v0.65.0 · github.comrefsource_MISC

Other CVEs in russh

All 24 →

8.3russh: Agent server never calls `Agent::confirm`, so keys added with the confirm constraint (`ssh-add -c`) sign without confirmation · CVE-2026-116794Oct 28 2.3pageant: unbounded frame buffering on peer-controlled 4-byte length prefix (memory-exhaustion DoS) · CVE-2026-116775Oct 27 4.3russh: peer-declared zero maximum packet size permanently stalls channel writes (silent AsyncWrite hang) · CVE-2026-116774Oct 27