/ 
Net-DNS-0.66_01
/ Net::DNS::RR::OPT
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::OPT - DNS OPT

SYNOPSIS

use Net::DNS::RR;

DESCRIPTION

Class for EDNS pseudo resource record OPT.

METHODS

This object should only be used inside the Net::DNS classes itself.

new

Since "OPT" is a pseudo record and should not be stored in masterfiles; Therefore we have not implemented a method to create this RR from string.

One may create the object from a hash. See RFC 2671 for details for the meaning of the hash keys.

$rr= Net::DNS::RR->new (
   name => "",                # Ignored and set to ""
   type => "OPT",  
   class => 1024,             # sets UDP payload size
   extendedrcode =>  0x00,    # sets the extended RCODE 1 octets
   ednsflags     =>  0x0000,  # sets the ednsflags (2octets)  
   optioncode   =>   0x0,     # 2 octets
   optiondata   =>   0x0      # optionlength octets
);

The ednsversion is set to 0 for now. The ttl value is determined from the extendedrcode, the ednsversion and the ednsflag. The rdata is constructed from the optioncode and optiondata see section 4.4 of RFC 2671

If optioncode is left undefined then we do not expect any RDATA.

The defaults are no rdata.

do, set_do, clear_do

$opt->set_do;

Reads, sets and clears the do flag. (first bit in the ednssflags);

size

   $opt->size(1498);
   print "Packet size:". $opt->size() ;

Sets or gets the packet size.

TODO

- This class is tailored to use with dnssec.

- Do some range checking on the input.

- This class probably needs subclasses once OPTION codes start to be defined.

- look at use of extended labels

COPYRIGHT

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

All Rights Reserved

Permission to use, copy, modify, and distribute this software and its documentation for any purpose and without fee is hereby granted, provided that the above copyright notice appear in all copies and that both that 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, written prior permission.

THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS; IN NO EVENT SHALL AUTHOR BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

Based on, and contains, code by Copyright (c) 1997-2002 Michael Fuhr.

SEE ALSO

perl(1), Net::DNS, Net::DNS::Resolver, Net::DNS::Packet, Net::DNS::Header, Net::DNS::Question, Net::DNS::RR, RFC 2435 Section 3