/ 
Net-DNS-1.49
/ Net::DNS::RR::SSHFP
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::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