Security Advisories (1)
CVE-2026-81928 (2026-09-01)

Net::DNS versions before 1.57 for Perl allow memory exhaustion via unbounded recursion in sig_data when re-encoding a message with a misplaced TSIG record. sig_data signs a message by re-encoding it, and removes TSIG records only from the additional section. A TSIG decoded into the answer or authority section survives that step and is signed again, so encoding re-enters sig_data with no termination condition. Decoding does not reject such a message: a TSIG that is not the last record on the wire raises "misplaced or corrupt TSIG", but the error is caught, reported as a warning, and the record is left in the packet. RFC 8945 section 5.2 requires the message to be dropped. The recursion is reached only when the decoded TSIG carries an empty MAC, since a MAC recovered from the wire short-circuits the signing step. It is reached only from code that re-encodes a message it decoded, such as a forwarder or a proxy. A decoded message that is never re-encoded is unaffected. Message direction does not matter: a query reaches the same path as a response. Each cycle re-encodes the whole message, so fewer than 100 bytes on the wire exhaust available memory and terminate the process.

NAME

Net::DNS::RR::OPT - DNS OPT resource record

SYNOPSIS

use Net::DNS;
my $packet = Net::DNS::Packet->new( ... );

$packet->header->do(1);		# extended header flag 

$packet->edns->UDPsize(1232);	# UDP payload size

$packet->edns->option( 'NSID' => {'OPTION-DATA' => 'rawbytes'} );
$packet->edns->option( 'DAU'  => [8, 10, 13, 14, 15, 16] );
$packet->edns->option( 'TCP-KEEPALIVE' => 200 );
$packet->edns->option( 'EXTENDED-ERROR' => {'INFO-CODE' => 123} );
$packet->edns->option( '65023' => {'BASE16' => '076578616d706c6500'} );

$packet->edns->print;

;; {	"EDNS-VERSION":	0,
;;	"FLAGS":	32768,
;;	"RCODE":	0,
;;	"UDPSIZE":	1232,
;;	"OPTIONS":	[
;;		{"NSID": "7261776279746573"},
;;		{"DAU": [ 8, 10, 13, 14, 15, 16 ]},
;;		{"TCP-KEEPALIVE": {"TIMEOUT": 200}},
;;		{"EXTENDED-ERROR": {"INFO-CODE": 123, "EXTRA-TEXT": ""}},
;;		{"65023": {"BASE16": "076578616d706c6500"}} ]
;;	}

DESCRIPTION

EDNS OPT pseudo resource record.

The OPT record supports EDNS protocol extensions and is not intended to be created, accessed or modified directly by user applications.

All EDNS features are performed indirectly by operations on the objects returned by the $packet->header and $packet->edns creator methods. The underlying mechanisms are, or should be, entirely hidden from the user.

METHODS

The available methods are those inherited from the base class augmented by the type-specific methods defined in this package.

Use of undocumented package features or direct access to internal data structures is discouraged and could result in program termination or other unpredictable behaviour.

version

$version = $packet->edns->version;

The version of EDNS supported by this OPT record.

UDPsize

$size = $packet->edns->UDPsize;
$packet->edns->UDPsize($size);

UDPsize() advertises the maximum size (octets) of UDP packet that can be reassembled in the network stack of the originating host.

rcode

$extended_rcode = $packet->header->rcode;

The 12 bit extended RCODE. The most significant 8 bits are obtained from the OPT record. The least significant 4 bits reside in the packet header.

flags

$do = $packet->header->do;
$packet->header->do(1);

$edns_flags = $packet->edns->flags;

16 bit field containing EDNS extended header flags.

options

my @options = $packet->edns->options;

When called in a list context, options() returns a list of option codes found in the OPT record.

option

my $octets = $packet->edns->option('COOKIE');
my $base16 = unpack 'H*', $octets;

When called in a scalar context with a single argument, option() returns the value of the specified option as an uninterpreted octet string. The method returns undef if the option is absent.

$packet->edns->option( 'COOKIE'	=> {'OPTION-DATA' => $octets} );
$packet->edns->option( '10'	=> {'BASE16' => $base16} );

An option can be added or replaced by providing the (name,value) pair. The option is deleted if the value is undefined.

my ($structure) = $packet->edns->option("DAU");
my $array	= $$structure{"DAU"};
my @algorithms	= @$array;

my ($structure) = $packet->edns->option(15);
my $table	= $$structure{"EXTENDED-ERROR"};
my $info_code	= $$table{'INFO-CODE'};
my $extra_text	= $$table{'EXTRA-TEXT'};

When called in a list context with a single argument, option() returns a structured representation of the specified option.

Similar forms of array or hash syntax may be used to construct the option value:

$packet->edns->option( 'DAU' => [8, 10, 13, 14, 15, 16] );

$packet->edns->option( 'EXTENDED-ERROR' => {
				'INFO-CODE'  => 123,
				'EXTRA-TEXT' => ""
				} );

COPYRIGHT

Copyright (c)2001,2002 RIPE NCC. Author Olaf M. Kolkman.

Portions Copyright (c)2012,2017-2026 Dick Franks.

All rights reserved.

Package template (c)2009,2012 O.M.Kolkman and R.W.Franks.

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::RR RFC6891 RFC3225