/ 
Net-DNS-0.42_02 UNAUTHORIZED RELEASE
/ Net::DNS::Header
Security Advisories (5)
CVE-2007-6341 (2008-02-08)

Allows remote attackers to cause a denial of service (program "croak") via a crafted DNS response.

CVE-2007-3409 (2007-06-26)

Net::DNS before 0.60, a Perl module, allows remote attackers to cause a denial of service (stack consumption) via a malformed compressed DNS packet with self-referencing pointers, which triggers an infinite loop.

CVE-2007-3377 (2007-06-25)

Header.pm in Net::DNS before 0.60, a Perl module, (1) generates predictable sequence IDs with a fixed increment and (2) can use the same starting ID for all child processes of a forking server, which allows remote attackers to spoof DNS responses, as originally reported for qpsmtp and spamassassin.

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::Header - DNS packet header class

SYNOPSIS

use Net::DNS::Header;

DESCRIPTION

A Net::DNS::Header object represents the header portion of a DNS packet.

METHODS

new

$header = Net::DNS::Header->new;
$header = Net::DNS::Header->new(\$data);

Without an argument, new creates a header object appropriate for making a DNS query.

If new is passed a reference to a scalar containing DNS packet data, it creates a header object from that data.

Returns undef if unable to create a header object (e.g., if the data is incomplete).

print

$header->print;

Dumps the header data to the standard output.

string

print $header->string;

Returns a string representation of the header object.

id

print "query id = ", $header->id, "\n";
$header->id(1234);

Gets or sets the query identification number.

qr

print "query response flag = ", $header->qr, "\n";
$header->qr(0);

Gets or sets the query response flag.

opcode

print "query opcode = ", $header->opcode, "\n";
$header->opcode("UPDATE");

Gets or sets the query opcode (the purpose of the query).

aa

print "answer is ", $header->aa ? "" : "non-", "authoritative\n";
$header->aa(0);

Gets or sets the authoritative answer flag.

tc

print "packet is ", $header->tc ? "" : "not ", "truncated\n";
$header->tc(0);

Gets or sets the truncated packet flag.

rd

print "recursion was ", $header->rd ? "" : "not ", "desired\n";
$header->rd(0);

Gets or sets the recursion desired flag.

cd

print "checking was ", $header->cd ? "not" : "", "desired\n";
$header->cd(0);

Gets or sets the checking disabled flag.

ra

print "recursion is ", $header->ra ? "" : "not ", "available\n";
$header->ra(0);

Gets or sets the recursion available flag.

print "The result has ", $header->ad ? "" : "not", "been verified\n"

Relevant in DNSSEC context.

(The AD bit is only set on answers where signatures have been cryptographically verified or the server is authoritative for the data and is allowed to set the bit by policy.)

rcode

print "query response code = ", $header->rcode, "\n";
$header->rcode("SERVFAIL");

Gets or sets the query response code (the status of the query).

qdcount, zocount

print "# of question records: ", $header->qdcount, "\n";
$header->qdcount(2);

Gets or sets the number of records in the question section of the packet. In dynamic update packets, this field is known as zocount and refers to the number of RRs in the zone section.

ancount, prcount

print "# of answer records: ", $header->ancount, "\n";
$header->ancount(5);

Gets or sets the number of records in the answer section of the packet. In dynamic update packets, this field is known as prcount and refers to the number of RRs in the prerequisite section.

nscount, upcount

print "# of authority records: ", $header->nscount, "\n";
$header->nscount(2);

Gets or sets the number of records in the authority section of the packet. In dynamic update packets, this field is known as upcount and refers to the number of RRs in the update section.

arcount, adcount

print "# of additional records: ", $header->arcount, "\n";
$header->arcount(3);

Gets or sets the number of records in the additional section of the packet. In dynamic update packets, this field is known as adcount.

data

$hdata = $header->data;

Returns the header data in binary format, appropriate for use in a DNS query packet.

COPYRIGHT

Copyright (c) 1997-2002 Michael Fuhr.

Portions Copyright (c) 2002-2003 Chris Reinhardt.

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, Net::DNS::Resolver, Net::DNS::Packet, Net::DNS::Update, Net::DNS::Question, Net::DNS::RR, RFC 1035 Section 4.1.1