/ 
Net-BitTorrent-v2.1.0
⭐ Starred 13 / Net::BitTorrent::DHT::Security
Security Advisories (2)
CVE-2026-57080 (2026-06-30)

Net::BitTorrent versions through 2.1.0 for Perl allow remote memory exhaustion via an uncapped peer-wire message-length prefix. The peer-wire framing in _process_messages trusts the 4-byte length prefix sent by a connected peer with no upper bound, while receive_data appends every inbound byte to the input buffer. A peer announces a length prefix of up to about 4 GiB and then streams bytes; the decoder waits until the buffer holds the full message before processing it, so the buffer grows without limit. Peer connections are unauthenticated, so any peer in the swarm exhausts the downloading process's memory. The largest legitimate message is a 16 KiB piece block, so any announced length far above that is anomalous.

CVE-2026-57081 (2026-06-30)

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.

NAME

Net::BitTorrent::DHT::Security - BEP 42 Security Extensions

SYNOPSIS

use Net::BitTorrent::DHT::Security;
my $sec = Net::BitTorrent::DHT::Security->new;

my $id = $sec->generate_node_id("127.0.0.1");
if ($sec->validate_node_id($id, "127.0.0.1")) {
    say "Node ID is valid for this IP";
}

DESCRIPTION

This module implements the security extensions defined in BEP 42. It provides methods for generating and validating Node IDs based on the node's IP address to prevent Sybil attacks and routing table poisoning.

CRC32c Implementation

This module includes a pure-Perl implementation of the CRC32c (Castagnoli) polynomial (0x82F63B78), which is required by BEP 42 for Node ID calculation.

METHODS

generate_node_id( $ip, [$seed] )

Generates a secure, BEP 42 compliant Node ID.

my $id = $sec->generate_node_id( '1.2.3.4' );

This method computes a node ID based on the provided IP address using the CRC32C algorithm as specified in BEP 42. This hardens the ID against Sybil attacks by binding it to the IP address.

Expected parameters:

$ip

String. The external IP address string (e.g., '1.2.3.4').

$seed - optional

A 1-byte integer seed (0-255). If omitted, a random one is used.

validate_node_id( $id_bin, $ip )

Validates a node ID against an IP address.

my $ok = $sec->validate_node_id( $id, $ip );

This method checks if the provided Node ID is valid for the given IP address according to BEP 42 criteria (matching the first 21 bits of the CRC32c hash).

Expected parameters:

$id_bin

String. The 20-byte binary node ID.

$ip

String. The IP address string associated with the node.

SEE ALSO

BEP 42: http://www.bittorrent.org/beps/bep_0042.html

AUTHOR

Sanko Robinson - https://github.com/sanko

COPYRIGHT

Copyright (C) 2008-2026 by Sanko Robinson.

This library is free software; you can redistribute it and/or modify it under the terms of the Artistic License 2.0.