Vulnerability · Published Oct 27, 2026 · Assigned by GitHub_M

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

Medium 4.3

In plain English

A medium-severity resource allocation without limits in russh from Eugeny. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 18% of all known vulnerabilities).

Severity (CVSS 3.1)4.3Medium

Exploit odds (30 days)0.3%top 82.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	rust-russh	no fix listed	DEBIAN-CVE-2026-116773
Ubuntu:26.10	rust-russh	no fix listed	UBUNTU-CVE-2026-116773

Affected products (as reported)

Vendor	Product	Versions
Eugeny	russh	< 0.65.0

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

References

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