/ 
Net-DNS-0.66
/ Net::DNS::Domain
Security Advisories (2)
CVE-2026-64193 (2026-07-20)

Net::DNS versions through 1.55 for Perl allow remote execution injection via EDNS EXTENDED ERROR. Net::DNS::RR::OPT::EXTENDED_ERROR::_decompose parses the EXTRA-TEXT field of an EDNS EXTENDED-ERROR option (RFC 8914) by tokenising the raw bytes and passing the result to Perl's eval. There is some escaping done for $ and @, but not for backticks. This can be exploited for command execution if $pkt->edns->option('EXTENDED-ERROR') is called in array context, for example with a payload of {0:`"<command>"`} in EXTRA-TEXT.

CVE-2026-64194 (2026-07-20)

Net::DNS versions through 1.55 for Perl allow Denial of Service via deep DNS compression pointer chains. Net::DNS::DomainName::decode follows RFC 1035 compression pointers by recursing into itself with no depth limit. It is possible to construct a name which saturates the call stack (at least with larger TCP responses), leading to a potential Denial of Service. The guard `$link < $offset` prevents forward and circular chains, but still allows arbitrarily long backward chains. The per-offset cache (`$cache`) is populated at the start of each call and short-circuits only re-traverses of the same offset - the initial descent through a fresh chain still recurses at full depth. A crafted packet can chain two-byte compression pointers so that each one points two bytes earlier than the previous, producing a chain length of `offset / 2`. For the 14-bit pointer field (max offset 16383) this gives up to ~8191 recursive frames. For a TCP DNS message the limit is the 16-bit length field (~32767 frames). Perl's default C stack handles only a few thousand frames; beyond that the process receives SIGSEGV or similar, which is a denial-of-service for any application parsing untrusted DNS data. The vulnerability is triggered by `Net::DNS::Packet->new(\$wire)` i.e. any point where the library decodes a DNS message from the network.

NAME

Net::DNS::Domain - Domain Name System domains

SYNOPSIS

use Net::DNS::Domain

DESCRIPTION

The Net::DNS::Domain module implements a class of abstract DNS domain objects with associated class and instance methods.

Each domain object instance represents a single DNS domain which has a fixed identity throughout its lifetime.

Internally, the primary representation is a (possibly empty) list of ASCII domain labels, and optional link to an ancestor domain object topologically closer to the root of the DNS namespace.

The presentation form of the domain name is generated on demand and the result cached within the object.

METHODS

new

$domain = new Net::DNS::Domain('example.com');

Creates a domain object which represents the DNS domain identified by the character string argument. The identifier consists of a sequence of labels delimited by dots.

The argument string consists of printable characters from the 7-bit ASCII repertoire.

A character preceded by \ represents itself, without any special interpretation.

Any 8-bit code point can be represented by \ followed by exactly three decimal digits. Character code points are ASCII, irrespective of the encoding employed by the underlying platform. No characters are associated with code points beyond 127.

Argument strings should be delimited by single quotes to avoid escape sequences being misinterpreted by the compiler.

The character string presentation format follows the conventions for zone files described in RFC1035.

decode

$domain = decode Net::DNS::Domain( \$buffer, $offset, $hash );

( $domain, $next ) = decode Net::DNS::Domain( \$buffer, $offset, $hash );

Creates a domain object which represents the DNS domain identified by the compressed name at the indicated offset within the data buffer.

The argument list consists of a reference to a scalar containing the wire-format data, specified offset and reference to a hash used to represent compressed names.

The returned offset value indicates the start of the next item in the data buffer.

encode

$data = $domain->encode( $offset, $hash );

Returns the wire-format representation of the domain object suitable for inclusion in a DNS packet buffer.

The optional arguments are the offset within the packet data where the domain name is to be stored and a reference to a hash table used to index compressed names within the packet.

name

$name = $domain->name;

Returns a character string corresponding to the "typical" form of domain name to which section 11 of RFC2181 alludes.

The string consists of printable characters from the 7-bit ASCII repertoire. Code points outside this set are represented by the appropriate numerical escape sequence.

mailbox

$mail = $domain->mailbox;

Returns a character string containing the mailbox interpretation of the domain name as described in RFC1035 section 8.

string

$fqdn = $domain->string;

Returns a character string containing the absolute name of the domain as described in RFC1035 section 5.1.

The string consists of printable characters from the 7-bit ASCII repertoire. Code points outside this set are represented by the appropriate numerical escape sequence.

Characters which have special meaning in a zone file, dots which are part of a domain label, and the escape character itself are represented by escape sequences which remove any such meaning.

BUGS

Platform-specific parts of the code are designed to be optimised away by the compiler for reasons of efficiency. This is achieved at considerable expense in terms of readability.

COPYRIGHT

Copyright (c)2009 Dick Franks.

All rights reserved.

This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.

SEE ALSO

perl(1), Net::DNS, RFC1035, RFC2181.