Vulnerability · Published May 8, 2026 · Assigned by GitHub_M

CVE-2026-42189Russh: Pre-auth DoS via unbounded allocation in keyboard-interactive auth

High 7.5

In plain English

A high-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 0.5% (higher than 42% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.5%top 58.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

Russh is a Rust SSH client & server library. Prior to version 0.60.1, a pre-authentication denial-of-service vulnerability exists in the server's keyboard-interactive authentication handler. A malicious client can crash any russh-based server that implements keyboard-interactive auth (e.g., for 2FA/TOTP) with a single malformed packet, requiring no credentials. This issue has been patched in version 0.60.1.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	rust-russh	0.64.1-1	DEBIAN-CVE-2026-42189
Ubuntu:26.10	rust-russh	no fix listed	UBUNTU-CVE-2026-42189

Affected products (as reported)

Vendor	Product	Versions
Eugeny	russh	< 0.60.1

Weakness: CWE-770, CWE-789 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/Eugeny/russh/security/advisories/GHSA-f5v4-2wr6-hqmg x_refsource_CONFIRM
https://github.com/Eugeny/russh/commit/6c3c80a9b6d60763d6227d60fa8310e57172a4d1 x_refsource_MISC
https://github.com/Eugeny/russh/releases/tag/v0.60.1 x_refsource_MISC