CVE-2026-57081
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk20th percentile - higher than 20% of all known CVEs
Summary
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.
Risk Assessment
An attacker can send a crafted .torrent file, magnet link, or DHT message, causing the BitTorrent client to exhaust RAM and crash. This can lead to a denial of service (DoS) for all users relying on the vulnerable library.
Recommendation
Immediately update Net::BitTorrent to version 2.2.0 or later, which includes a fix limiting recursion depth. If an update is not possible, deploy firewall rules to filter suspicious DHT packets and .torrent files with excessive nesting depth.
Other vulnerabilities in Net::BitTorrent
See all- CVE-2026-57082Medium
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.
- 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 through 2.1.0 for Perl allow remote memory exhaustion via deeply nested bencoded input. bdecode recurses once per nested list or dictionary level with no depth cap, and each recursive call receives the remaining buffer by value while the list and dictionary branches capture the whole remainder, so every live recursion frame keeps its own copy of the shrinking buffer (O(N^2) bytes for an N-deep input). The decoder runs on every untrusted bencode source: .torrent files, BEP09 metadata fetched from peers, DHT messages, and tracker responses. A bencoded input of roughly 150,000 nested lists (about 150 KB on the wire) drives multi-gigabyte peak memory, so one short message from any peer, or one crafted .torrent file or magnet link, terminates the client.