CVE-2026-73430: CWE-754: Improper Check for Unusual or Exceptional Conditions in Eugeny russh
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.
AI Analysis
Technical Summary
The vulnerability in russh occurs because the server accepts an all-zero peer public value during the Curve25519 key exchange, leading to the computation of an all-zero shared secret. Subsequently, the function compute_exchange_hash calls encode_mpint, which indexes beyond the end of the input while skipping leading zero bytes, causing a panic. This panic happens before client authentication, allowing an unauthenticated attacker to cause a denial of service by terminating the server key-exchange task. The flaw is identified as CWE-754 (Improper Check for Unusual or Exceptional Conditions) and affects russh versions prior to 0.62.4.
Potential Impact
An unauthenticated attacker can cause a denial of service by sending a malformed SSH key exchange initiation message, which triggers a panic in the server and terminates the key-exchange task. This disrupts the availability of the SSH service. There is no impact on confidentiality or integrity.
Mitigation Recommendations
This vulnerability is fixed in russh version 0.62.4. Users should upgrade to version 0.62.4 or later to remediate the issue. No other mitigation or workaround is indicated.
CVE-2026-73430: CWE-754: Improper Check for Unusual or Exceptional Conditions in Eugeny russh
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 v3.1
Score 5.3medium
Affected software
Eugeny
russh
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in russh occurs because the server accepts an all-zero peer public value during the Curve25519 key exchange, leading to the computation of an all-zero shared secret. Subsequently, the function compute_exchange_hash calls encode_mpint, which indexes beyond the end of the input while skipping leading zero bytes, causing a panic. This panic happens before client authentication, allowing an unauthenticated attacker to cause a denial of service by terminating the server key-exchange task. The flaw is identified as CWE-754 (Improper Check for Unusual or Exceptional Conditions) and affects russh versions prior to 0.62.4.
Potential Impact
An unauthenticated attacker can cause a denial of service by sending a malformed SSH key exchange initiation message, which triggers a panic in the server and terminates the key-exchange task. This disrupts the availability of the SSH service. There is no impact on confidentiality or integrity.
Mitigation Recommendations
This vulnerability is fixed in russh version 0.62.4. Users should upgrade to version 0.62.4 or later to remediate the issue. No other mitigation or workaround is indicated.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-08-12T14:32:11.796Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 6a7ce1eabf8831d5392b0356
Added to database: 08/12/2026, 21:13:14 UTC
Last enriched: 08/12/2026, 21:27:53 UTC
Last updated: 09/25/2026, 15:46:00 UTC
Views: 60
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