/ 
Net-DNS-1.42_04
/ 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 = Net::DNS::Question->new('example.com', 'AAAA', 'IN');

DESCRIPTION

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

METHODS

new

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

$question = Net::DNS::Question->new('2001::DB8::dead:beef', 'PTR', 'IN');
$question = Net::DNS::Question->new('2001::DB8::dead:beef');

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

($question, $offset) = Net::DNS::Question->decode(\$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.

string

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

Returns a string representation of the question record.

print

$object->print;

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

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

qname, zname

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

Fully qualified domain name in the form required for a query transmitted to a nameserver. In dynamic update packets, this attribute is known as zname() and refers to the zone name.

qtype, ztype, type

$qtype = $question->type;
$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, class

$qclass = $question->class;
$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.

COPYRIGHT

Copyright (c)1997-2000 Michael Fuhr.

Portions Copyright (c)2002,2003 Chris Reinhardt.

Portions Copyright (c)2003,2006-2011 Dick Franks.

All rights reserved.

LICENSE

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the original copyright notices appear in all copies and that both copyright notice and this permission notice appear in supporting documentation, and that the name of the author not be used in advertising or publicity pertaining to distribution of the software without specific prior written permission.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

SEE ALSO

perl Net::DNS Net::DNS::DomainName Net::DNS::Packet RFC1035(4.1.2)