/ 
Net-DNS-0.79_1
/ Net::DNS::Question
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::Question - DNS question record

SYNOPSIS

use Net::DNS::Question;

$question = new Net::DNS::Question('example.com', 'A', 'IN');

DESCRIPTION

A Net::DNS::Question object represents a record in the question section of a DNS packet.

METHODS

new

$question = new Net::DNS::Question('example.com', 'A', 'IN');
$question = new Net::DNS::Question('example.com');

$question = new Net::DNS::Question('192.0.32.10', 'PTR', 'IN');
$question = new Net::DNS::Question('192.0.32.10');

Creates a question object from the domain, type, and class passed as arguments. One or both type and class arguments may be omitted and will assume the default values shown above.

RFC4291 and RFC4632 IP address/prefix notation is supported for queries in both in-addr.arpa and ip6.arpa namespaces.

decode

$question = decode Net::DNS::Question(\$data, $offset);

($question, $offset) = decode Net::DNS::Question(\$data, $offset);

Decodes the question record at the specified location within a DNS wire-format packet. The first argument is a reference to the buffer containing the packet data. The second argument is the offset of the start of the question record.

Returns a Net::DNS::Question object and the offset of the next location in the packet.

An exception is raised if the object cannot be created (e.g., corrupt or insufficient data).

encode

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

Returns the Net::DNS::Question in binary format suitable for inclusion in a DNS packet buffer.

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

name

$name = $question->name;

Internationalised domain name corresponding to the qname attribute.

Decoding non-ASCII domain names is computationally expensive and undesirable for names which are likely to be used to construct further queries.

When required to communicate with humans, the 'proper' domain name should be extracted from a query or reply packet.

$query = new Net::DNS::Packet( $example, 'ANY' );
$reply = $resolver->send($query) or die;
($question) = $reply->question;
$name = $question->name;

qname, zname

$qname = $question->qname;
$zname = $question->zname;

Canonical ASCII domain name as required for the query subject transmitted to a nameserver. In dynamic update packets, this attribute is known as zname() and refers to the zone name.

qtype, ztype

$qtype = $question->qtype;
$ztype = $question->ztype;

Returns the question type attribute. In dynamic update packets, this attribute is known as ztype() and refers to the zone type.

qclass, zclass

$qclass = $question->qclass;
$zclass = $question->zclass;

Returns the question class attribute. In dynamic update packets, this attribute is known as zclass() and refers to the zone class.

print

$object->print;

Prints the record to the standard output. Calls the string() method to get the string representation.

string

print "string = ", $question->string, "\n";

Returns a string representation of the question record.

COPYRIGHT

Copyright (c)1997-2002 Michael Fuhr.

Portions Copyright (c)2002-2004 Chris Reinhardt.

Portions Copyright (c)2003,2006-2011 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, Net::DNS, Net::DNS::DomainName, Net::DNS::Packet, RFC 1035 Section 4.1.2