/ 
Net-DNS-0.58
/ Net::DNS::RR::TSIG
Security Advisories (6)
CVE-2007-6341 (2008-02-08)

Allows remote attackers to cause a denial of service (program "croak") via a crafted DNS response.

CVE-2007-3409 (2007-06-26)

Net::DNS before 0.60, a Perl module, allows remote attackers to cause a denial of service (stack consumption) via a malformed compressed DNS packet with self-referencing pointers, which triggers an infinite loop.

CVE-2007-3377 (2007-06-25)

Header.pm in Net::DNS before 0.60, a Perl module, (1) generates predictable sequence IDs with a fixed increment and (2) can use the same starting ID for all child processes of a forking server, which allows remote attackers to spoof DNS responses, as originally reported for qpsmtp and spamassassin.

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.

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::TSIG - DNS TSIG resource record

SYNOPSIS

use Net::DNS::RR;

DESCRIPTION

Class for DNS Transaction Signature (TSIG) resource records.

METHODS

algorithm

$rr->algorithm($algorithm_name);
print "algorithm = ", $rr->algorithm, "\n";

Gets or sets the domain name that specifies the name of the algorithm. The only algorithm currently supported is HMAC-MD5.SIG-ALG.REG.INT.

time_signed

$rr->time_signed(time);
print "time signed = ", $rr->time_signed, "\n";

Gets or sets the signing time as the number of seconds since 1 Jan 1970 00:00:00 UTC.

The default signing time is the current time.

fudge

$rr->fudge(60);
print "fudge = ", $rr->fudge, "\n";

Gets or sets the "fudge", i.e., the seconds of error permitted in the signing time.

The default fudge is 300 seconds.

mac_size

print "MAC size = ", $rr->mac_size, "\n";

Returns the number of octets in the message authentication code (MAC). The programmer must call a Net::DNS::Packet object's data method before this will return anything meaningful.

mac

print "MAC = ", $rr->mac, "\n";

Returns the message authentication code (MAC) as a string of hex characters. The programmer must call a Net::DNS::Packet object's data method before this will return anything meaningful.

original_id

$rr->original_id(12345);
print "original ID = ", $rr->original_id, "\n";

Gets or sets the original message ID.

error

print "error = ", $rr->error, "\n";

Returns the RCODE covering TSIG processing. Common values are NOERROR, BADSIG, BADKEY, and BADTIME. See RFC 2845 for details.

other_len

print "other len = ", $rr->other_len, "\n";

Returns the length of the Other Data. Should be zero unless the error is BADTIME.

other_data

print "other data = ", $rr->other_data, "\n";

Returns the Other Data. This field should be empty unless the error is BADTIME, in which case it will contain the server's time as the number of seconds since 1 Jan 1970 00:00:00 UTC.

sig_data

my $sigdata = $tsig->sig_data($packet);

Returns the packet packed according to RFC2845 in a form for signing. This is only needed if you want to supply an external signing function, such as is needed for TSIG-GSS.

sign_func

     sub my_sign_fn($$) {
	     my ($key, $data) = @_;
	     
	     return some_digest_algorithm($key, $data);
     }

     $tsig->sign_func(\&my_sign_fn);

This sets the signing function to be used for this TSIG record.

The default signing function is HMAC-MD5.

BUGS

This code is still under development. Use with caution on production systems.

The time_signed and other_data fields should be 48-bit unsigned integers (RFC 2845, Sections 2.3 and 4.5.2). The current implementation ignores the upper 16 bits; this will cause problems for times later than 19 Jan 2038 03:14:07 UTC.

The only builtin algorithm currently supported is HMAC-MD5.SIG-ALG.REG.INT. You can use other algorithms by supplying an appropriate sign_func.

COPYRIGHT

Copyright (c) 2002 Michael Fuhr.

Portions Copyright (c) 2002-2004 Chris Reinhardt.

All rights reserved. This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.

ACKNOWLEDGMENT

Most of the code in the Net::DNS::RR::TSIG module was contributed by Chris Turbeville.

Support for external signing functions was added by Andrew Tridgell.

SEE ALSO

perl(1), Net::DNS, Net::DNS::Resolver, Net::DNS::Packet, Net::DNS::Header, Net::DNS::Question, Net::DNS::RR, RFC 2845