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Net-BitTorrent-v2.1.0
⭐ Starred 13 / Net::BitTorrent::Protocol::BEP03::Bencode
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::Protocol::BEP03::Bencode - BitTorrent Bencode Encoder/Decoder

SYNOPSIS

use Net::BitTorrent::Protocol::BEP03::Bencode qw[bencode bdecode];

my $raw = bencode( { a => [1, 2, 3] } );
my $data = bdecode( $raw );

DESCRIPTION

Bencoding is the BitTorrent protocol's basic serialization and data organization format. The specification supports integers, lists (arrays), dictionaries (hashes), and byte strings. This module implements the format used for metadata and protocol messages.

FUNCTIONS

By default, nothing is exported. You may import any of the following functions by name or with the :all tag.

bencode( $data )

Encodes a Perl data structure into a bencoded string.

my $raw = bencode( { a => [1, 2, 3] } );

This method handles scalars (strings and integers), array references, and hash references.

Expected parameters:

$data

The Perl data structure to encode (basic scalar, array reference, or hash reference).

bdecode( $string, [$want_leftover] )

Decodes a bencoded string into a Perl data structure.

my $data = bdecode( $raw );

Expected parameters:

$string

The bencoded binary string.

$want_leftover - optional

If true, returns a list containing the decoded data and the remaining string.

This function will die on malformed data.

SEE ALSO

The BitTorrent Protocol Specification

https://bittorrent.org/beps/bep_0003.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.