Vulnerability · Published Sep 29, 2026 · Assigned by GitHub_M

CVE-2026-102822russh: negotiating a MAC-requiring block cipher (CTR/CBC) with mac=none causes a slice-index-out-of-range panic

Low 3.7

In plain English

A low-severity security flaw 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 26% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)3.7Low

Exploit odds (30 days)0.3%top 74.1% 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, a connection configured to permit mac=none can negotiate it with a MAC-requiring CTR or CBC block cipher because the selection logic validates needs_mac() only when MAC selection fails. A remote peer can then send a packet with a decrypted length of zero, causing russh/src/cipher/mod.rs to shrink the previously read block before indexing buffer.buffer[16..], which panics and terminates the connection task. 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-2026-102822
Ubuntu:26.10	rust-russh	no fix listed	UBUNTU-CVE-2026-102822

Affected products (as reported)

Vendor	Product	Versions
Eugeny	russh	< 0.63.1

Weakness: CWE-129 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

References

https://github.com/Eugeny/russh/security/advisories/GHSA-p8qx-h547-fjw9 x_refsource_CONFIRM
https://github.com/Eugeny/russh/commit/2885385abfee279092a41d80c6cb6ac367353159 x_refsource_MISC
https://github.com/Eugeny/russh/releases/tag/v0.63.1 x_refsource_MISC