Vulnerability · Published Aug 12, 2026 · Assigned by GitHub_M

CVE-2026-73430Russh: Pre-auth remote panic via all-zero Curve25519 peer public value (encode_mpint OOB)

Medium 5.3

In plain English

A medium-severity security flaw in russh from Eugeny. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.6% (higher than 49% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium

Exploit odds (30 days)0.6%top 51.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Russh is a Rust SSH client & server library. Prior to 0.62.4, an unauthenticated SSH client can cause a denial of service by sending SSH_MSG_KEX_ECDH_INIT with a 32-byte all-zero Q_C value. Curve25519Kex::server_dh in russh/src/kex/curve25519.rs accepts the all-zero peer public value and computes an all-zero shared secret, after which compute_exchange_hash calls encode_mpint in russh/src/kex/mod.rs and indexes beyond the end of the input while skipping leading zero bytes. The resulting panic occurs before authentication and terminates the server key-exchange task. This issue is fixed in version 0.62.4.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	rust-russh	0.64.1-1	DEBIAN-CVE-2026-73430
Ubuntu:26.10	rust-russh	no fix listed	UBUNTU-CVE-2026-73430

Affected products (as reported)

Vendor	Product	Versions
Eugeny	russh	< 0.62.4

Weakness: CWE-754 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References

https://github.com/Eugeny/russh/security/advisories/GHSA-5xvq-cp9x-6p6r x_refsource_CONFIRM
https://github.com/Eugeny/russh/commit/a7fc1eb5717264e31c3c5f7dd849b73989a08f3d x_refsource_MISC
https://github.com/Eugeny/russh/releases/tag/v0.62.4 x_refsource_MISC