CVE-2022-29245

Summary

SSH.NET is a Secure Shell (SSH) library for .NET. In versions 2020.0.0 and 2020.0.1, during an X25519 key exchange, the client’s private key is generated with System.Random. System.Random is not a cryptographically secure random number generator, it must therefore not be used for cryptographic purposes. When establishing an SSH connection to a remote host, during the X25519 key exchange, the private key is generated with a weak random number generator whose seed can be brute forced. This allows an attacker who is able to eavesdrop on the communications to decrypt them. Version 2020.0.2 contains a patch for this issue. As a workaround, one may disable support for curve25519-sha256 and curve25519-sha256@libssh.org key exchange algorithms.

Affected Software

Weaknesses

• CWE-338: CWE-338: Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)

ADP Enrichment

CVE Program Container

Additional References

• https://github.com/sshnet/SSH.NET/security/advisories/GHSA-72p8-v4hg-v45p
• https://github.com/sshnet/SSH.NET/commit/03c6d60736b8f7b42e44d6989a53f9b644a091fb
• https://github.com/sshnet/SSH.NET/blob/bc99ada7da3f05f50d9379f2644941d91d5bf05a/src/Renci.SshNet/Security/KeyExchangeECCurve25519.cs#L51
• https://github.com/sshnet/SSH.NET/releases/tag/2020.0.2

CISA ADP Vulnrichment

• SSVC:
• Exploitation: poc
  • Automatable: no
  • Technical Impact: partial

References

• https://github.com/sshnet/SSH.NET/security/advisories/GHSA-72p8-v4hg-v45p
• https://github.com/sshnet/SSH.NET/commit/03c6d60736b8f7b42e44d6989a53f9b644a091fb
• https://github.com/sshnet/SSH.NET/blob/bc99ada7da3f05f50d9379f2644941d91d5bf05a/src/Renci.SshNet/Security/KeyExchangeECCurve25519.cs#L51
• https://github.com/sshnet/SSH.NET/releases/tag/2020.0.2

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