Vulnerability · Published Sep 29, 2026 · Assigned by GitHub_M

CVE-2026-102823russh: Client-side channel-scoped Handler callbacks fire for channel IDs the client never opened

High 7.5

In plain English

A high-severity improper input validation 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 25% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.3%top 75.2% 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. Prior to 0.63.1, client_read_authenticated in russh/src/client/encrypted.rs forwards CHANNEL_DATA, CHANNEL_EXTENDED_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_OPEN_FAILURE, CHANNEL_SUCCESS, CHANNEL_FAILURE, and CHANNEL_REQUEST subtypes exit-status, exit-signal, and xon-xoff to public client::Handler callbacks without confirming that the ChannelId belongs to a channel the client opened and established. A malicious SSH server can send lifecycle events for predicted, unopened, unconfirmed, or released channel identifiers, causing application panics or corrupting command completion and exit-code tracking. This issue is fixed in version 0.63.1.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	rust-russh	0.64.1-1	DEBIAN-CVE-2026-102823
Ubuntu:26.10	rust-russh	no fix listed	UBUNTU-CVE-2026-102823

Affected products (as reported)

Vendor	Product	Versions
Eugeny	russh	< 0.63.1

Weakness: CWE-20 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

https://github.com/Eugeny/russh/security/advisories/GHSA-47hw-gvq5-r2gm x_refsource_CONFIRM
https://github.com/Eugeny/russh/commit/3430fd26ecafc0dc3705210f5f39a9119fa22774 x_refsource_MISC
https://github.com/Eugeny/russh/releases/tag/v0.63.1 x_refsource_MISC