Medium severity · published Aug 12, 2026
CVE-2026-73430
Russh: Pre-auth remote panic via all-zero Curve25519 peer public value (encode_mpint OOB)
5.3
CVSS
0.6%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 48% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RU
russh · Eugeny
< 0.62.4 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-73430
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-73430
github.com
https://github.com/Eugeny/russh/commit/a7fc1eb5717264e31c3c5f7dd849b73989a08f3d
github.com
https://github.com/Eugeny/russh/releases/tag/v0.62.4
github.com
https://github.com/Eugeny/russh/security/advisories/GHSA-5xvq-cp9x-6p6r
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