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::SSHFP - DNS SSHFP resource record

SYNOPSIS

use Net::DNS;
$rr = Net::DNS::RR->new('name SSHFP algorithm fptype fp');

DESCRIPTION

DNS SSH Fingerprint (SSHFP) resource records.

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.

algorithm

$algorithm = $rr->algorithm;
$rr->algorithm( $algorithm );

The 8-bit algorithm number describes the algorithm used to construct the public key.

fptype

$fptype = $rr->fptype;
$rr->fptype( $fptype );

The 8-bit fingerprint type number describes the message-digest algorithm used to calculate the fingerprint of the public key.

fingerprint

fp

$fp = $rr->fp;
$rr->fp( $fp );

Hexadecimal representation of the fingerprint digest.

fpbin

$fpbin = $rr->fpbin;
$rr->fpbin( $fpbin );

Returns opaque octet string representing the fingerprint digest.

babble

print $rr->babble;

The babble() method returns the 'BabbleBubble' representation of the fingerprint if the Digest::BubbleBabble package is available, otherwise an empty string is returned.

Bubble babble represents a message digest as a string of "real" words, to make the fingerprint easier to remember. The "words" are not necessarily real words, but they look more like words than a string of hex characters.

Bubble babble fingerprinting is used by the SSH2 suite (and consequently by Net::SSH::Perl, the Perl SSH implementation) to display easy-to-remember key fingerprints.

The 'BubbleBabble' string is appended as a comment when the string method is called.

COPYRIGHT

Copyright (c)2007 Olaf Kolkman, NLnet Labs.

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 RFC4255