# CVE-2026-116773: russh memory exhaustion via unbounded EXT_INFO packets

Source: https://junglewise.ai/threats/cve-2026-116773-russh-is-a-rust-ssh-client-and-server-library-that-includes-an  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-116773 · Severity: medium · CVSS 4.3 · Published 2026-10-27

russh is a Rust SSH client library that failed to limit the number of extension information messages an SSH server could send. A malicious SSH server can repeatedly send crafted extension packets to exhaust the client's memory over time, causing the client to become unresponsive or crash. This affects any application using russh as an SSH client before version 0.65.0.

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-2026-116773 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-116773 being exploited in the wild.

**How severe is CVE-2026-116773?** Medium severity, with a CVSS score of 4.3, published 27 October 2026.

**Which products and versions are affected?** russh (crates.io) < 0.65, ECOSYSTEM:introduced=0,fixed=0.65; Russh before 0.65.0.

**Is there a fix for CVE-2026-116773?** Yes. russh (crates.io): upgrade to 0.65 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-116773 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-116773?** Check whether you run russh (crates.io) or Russh 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 0.65 or later

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


## Technical details

A use-after-free in the client's Session::process_packet handler accepts unlimited private message number 7 (EXT_INFO) packets before authentication completes. The handle_ext_info function appends extension names to received_extensions without bounds checking or deduplication, allowing a malicious server to trigger progressive memory exhaustion. The fix applies rate-limiting to EXT_INFO message processing.

## Affected products

- russh russh before 0.65.0

## Identifiers

- CVE-2026-116773
- GHSA-4p9f-7p9m-5vfg

## Timeline

- 2026-10-27: advisory
- 2026-10-25: patched

## References

- [https://github.com/Eugeny/russh/commit/b33e93beec393e6d29eee69c1b8831736724ee75](https://github.com/Eugeny/russh/commit/b33e93beec393e6d29eee69c1b8831736724ee75)
- [https://github.com/Eugeny/russh/releases/tag/v0.65.0](https://github.com/Eugeny/russh/releases/tag/v0.65.0)

## 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'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)
- [russh SSH agent unbounded memory allocation via constraint records](https://junglewise.ai/threats/cve-2026-111061-russh-is-a-rust-ssh-client-and-server-library-that-includes-an)