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

Source: https://junglewise.ai/threats/cve-2026-102822-russh-is-a-rust-ssh-client-and-server-library-prior-to-0-63-1-a  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-29  
License: CC BY 4.0 with a link back

CVE-2026-102822 · Severity: low · CVSS 3.7 · Published 2026-09-29

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.

Technologies: [russh (crates.io)](https://junglewise.ai/threats/technologies/crates-io-russh). Vendors: [crates.io](https://junglewise.ai/threats/vendors/crates-io).

## Quick answers

**Is CVE-2026-102822 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-102822 being exploited in the wild.

**How severe is CVE-2026-102822?** Low severity, with a CVSS score of 3.7, published 29 September 2026.

**Which products and versions are affected?** russh (crates.io) <= 0.63.0, SEMVER:introduced=0,fixed=0.63.1.

**Is there a fix for CVE-2026-102822?** Yes. russh (crates.io): upgrade to 0.63.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2026-102822?** Check whether you run russh (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- russh (crates.io): upgrade to 0.63.1 or later

  ```sh
  cargo update -p russh
  ```


## Affected products

- russh (crates.io) <= 0.63.0, SEMVER:introduced=0,fixed=0.63.1

## Identifiers

- CVE-2026-102822
- GHSA-p8qx-h547-fjw9

## Related threats

- [russh SSH server signature algorithm mismatch in publickey auth](https://junglewise.ai/threats/cve-2026-111062-a-russh-ssh-server-accepts-a-publickey-authentication-whose)
- [russh SSH agent confirmation bypass](https://junglewise.ai/threats/cve-2026-116794-russh-is-a-rust-ssh-client-and-server-library-that-includes-an)
- [russh SSH library zero maximum packet size denial of service](https://junglewise.ai/threats/cve-2026-116774-russh-is-a-rust-ssh-client-and-server-library-that-includes-an)
- [russh memory exhaustion via unbounded EXT_INFO packets](https://junglewise.ai/threats/cve-2026-116773-russh-is-a-rust-ssh-client-and-server-library-that-includes-an)
- [russh's SSH agent server is susceptible to unbound allocations via repeated SSH_AGENT_CONSTRAIN_CONFIRM messages](https://junglewise.ai/threats/cve-2026-116696-russh-is-a-rust-ssh-client-and-server-library-that-includes-an)