Vulnerability Description
Net::BitTorrent versions before 2.1.0 for Perl generate the MSE Diffie-Hellman private key with a non-cryptographic PRNG. The MSE (Message Stream Encryption) handshake derives its 160-bit Diffie-Hellman private key from Perl's rand(), a non-cryptographic drand48-class generator seeded once per process, in KeyExchange.pm. The shared secret and the RC4 keys derived from it (the SHA-1 of "keyA" or "keyB", the shared secret, and the infohash) therefore depend entirely on a predictable PRNG. The same handshake sends, in cleartext, random padding drawn from the same rand() sequence in _random_pad, immediately after the public key and the private-key draw. A passive observer of the handshake recovers the PRNG state from the cleartext padding, reconstructs the private key, computes the shared secret from the peer's public key on the wire, derives the RC4 keys, and decrypts the connection, defeating the passive-observation obfuscation MSE provides.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/sanko/Net-BitTorrent.pm/security/advisories/GHSA-g444-x2c5-94
- https://metacpan.org/release/SANKO/Net-BitTorrent-v2.1.0/changes
FAQ
What is CVE-2026-57082?
CVE-2026-57082 is a vulnerability with a CVSS score of 5.9 (MEDIUM). Net::BitTorrent versions before 2.1.0 for Perl generate the MSE Diffie-Hellman private key with a non-cryptographic PRNG. The MSE (Message Stream Encryption) handshake derives its 160-bit Diffie-Hell...
How severe is CVE-2026-57082?
CVE-2026-57082 has been rated MEDIUM with a CVSS base score of 5.9/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-57082?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.