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::Text - DNS text representation

SYNOPSIS

use Net::DNS::Text;

$object = Net::DNS::Text->new('example');
$string = $object->string;

$object = Net::DNS::Text->decode( \$data, $offset );
( $object, $next ) = Net::DNS::Text->decode( \$data, $offset );

$data = $object->encode;
$text = $object->value;

DESCRIPTION

The Net::DNS::Text module implements a class of text objects with associated class and instance methods.

Each text object instance has a fixed identity throughout its lifetime.

METHODS

new

$object = Net::DNS::Text->new('example');

Creates a text object which encapsulates a single character string component of a resource record.

Arbitrary single-byte characters can be represented by \ followed by exactly three decimal digits. Such characters are devoid of any special meaning.

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

decode

$object = Net::DNS::Text->decode( \$buffer, $offset );

( $object, $next ) = Net::DNS::Text->decode( \$buffer, $offset );

Creates a text object which represents the decoded data at the indicated offset within the data buffer.

The argument list consists of a reference to a scalar containing the wire-format data and offset of the text data.

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

encode

$data = $object->encode;

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

raw

$data = $object->raw;

Returns the wire-format encoded representation of the text object without the explicit length field.

value

$value = $text->value;

Character string representation of the text object.

string

$string = $text->string;

Conditionally quoted RFC1035 zone file representation of the text object.

unicode

$string = $text->unicode;

Conditionally quoted Unicode representation of the text object.

BUGS

Coding strategy is intended to avoid creating unnecessary argument lists and stack frames. This improves efficiency at the expense of code readability.

Platform specific character coding features are conditionally compiled into the code.

COPYRIGHT

Copyright (c)2009-2011 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 RFC1035 RFC3629