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Net-BitTorrent-v2.1.0
⭐ Starred 13 / Net::BitTorrent::Tracker::UDP
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::Tracker::UDP - UDP BitTorrent Tracker Protocol (BEP 15)

SYNOPSIS

use Net::BitTorrent::Tracker::UDP;

my $tracker = Net::BitTorrent::Tracker::UDP->new(
    url => 'udp://tracker.openbittorrent.com:80/announce'
);

# Announce
$tracker->perform_announce({
    infohash   => $bin_ih,
    peer_id    => $my_id,
    port       => 6881,
    downloaded => 0,
    uploaded   => 0,
    left       => 1024
}, sub ($res) {
    say 'Peers: ' . join(', ', map { $_->{ip} } @{$res->{peers}});
});

DESCRIPTION

Net::BitTorrent::Tracker::UDP implements the lightweight UDP Tracker Protocol (BEP 15). UDP is the preferred transport for BitTorrent trackers as it significantly reduces overhead on the tracker server compared to HTTP.

BitTorrent v2 Support

This module is BEP 52 compliant. It handles 32-byte SHA-256 infohashes by dynamically adjusting the binary structure of outgoing messages or by providing truncated/hashed 20-byte identifiers where necessary for legacy compatibility.

METHODS

perform_announce( \%params, [$callback] )

Sends an announce request to the UDP tracker.

$tracker->perform_announce( \%params, sub ($res) { ... } );

This method handles connection ID acquisition and retransmissions automatically.

Expected parameters:

\%params

Standard announce parameters (infohash, peer_id, port, uploaded, downloaded, left, event).

$callback - optional

Called with the parsed response hash containing interval, leechers, seeders, and peers.

perform_scrape( \@infohashes, [$callback] )

Sends a scrape request to the UDP tracker.

$tracker->perform_scrape( \@ihs, sub ($res) { ... } );

Expected parameters:

\@infohashes

List of binary infohashes to scrape.

$callback - optional

Called with the scrape results.

tick( )

Performs periodic maintenance.

$tracker->tick( 0.1 );

This method handles incoming packets and retransmissions for pending requests.

receive_data( $data )

Processes an incoming UDP packet.

$tracker->receive_data( $raw_packet );

Expected parameters:

$data

The raw packet payload.

url( )

Returns the tracker URL.

Specifications

  • BEP 15: UDP Tracker Protocol

  • BEP 52: The BitTorrent Protocol v2 (UDP extensions)

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.