CVE-2026-57082
MediumCVSS 5.9Exploitation Probability (EPSS)
Low risk7th percentile - higher than 7% of all known CVEs
Summary
The vulnerability in Net::BitTorrent for Perl before version 2.1.0 generates the MSE Diffie-Hellman private key using a non-cryptographic PRNG based on rand(). This allows a passive observer to recover the PRNG state from cleartext padding, then compute the private key and decrypt the connection.
Risk Assessment
Organizations using the vulnerable Net::BitTorrent version risk complete bypass of MSE protection, enabling a passive attacker to decrypt all BitTorrent traffic, potentially including sensitive data exchanged between clients.
Recommendation
Immediately update Net::BitTorrent to version 2.1.0 or later, which uses a cryptographically secure random number generator for Diffie-Hellman key generation.
Other vulnerabilities in Net::BitTorrent
See all- CVE-2026-57081High
A vulnerability in the Net::BitTorrent library for Perl (up to version 2.1.0) allows remote memory exhaustion via deeply nested bencoded input. The decoder has no recursion depth limit, and each recursion level keeps a copy of the buffer, causing quadratic memory consumption.
- CVE-2026-57080High
In the Net::BitTorrent library for Perl versions up to and including 2.1.0, there is a remote memory exhaustion vulnerability. The issue is the lack of an upper bound on the message-length prefix in the peer-wire framing, allowing a malicious peer to send a huge prefix and stream data, causing unbounded growth of the input buffer.
- CVE-2026-57079Medium
A vulnerability in Net::BitTorrent for Perl before version 2.1.0 allows writing files outside the download directory via path traversal in peer-supplied metadata. An attacker can exploit the ut_metadata extension (BEP09) to supply file names containing ".." sequences, bypassing path validation.
Original NVD description (English source)
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.