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perl-5.45.1
⭐ Starred 2013 / Net::hostent
Security Advisories (1)
CVE-2026-15534 (2026-08-09)

Perl versions through 5.45.1 have out-of-bounds heap reads and writes during regular expression matching via an undersized superlinear cache in S_regmatch. The regex engine's superlinear cache holds one bit per subject position for each participating WHILEM node, so the bit count is the subject length plus one times the number of nodes. Nothing checks that product for positive overflow of the signed 32-bit count: a 286331153 byte subject matched against a pattern with 15 participating nodes stores the count as 14, leaving a two byte cache. The cache is then indexed from the real match position and node number, so reads go past the end of the allocation, and on failure CACHEsayNO sets a bit past it. A caller that matches an attacker controlled subject of this size against a pattern of this shape can crash the process or corrupt heap memory.

NAME

Net::hostent - by-name interface to Perl's built-in gethost*() functions

SYNOPSIS

use Net::hostent;

DESCRIPTION

This module's default exports override the core gethostbyname() and gethostbyaddr() functions, replacing them with versions that return "Net::hostent" objects. This object has methods that return the similarly named structure field name from the C's hostent structure from netdb.h; namely name, aliases, addrtype, length, and addr_list. The aliases and addr_list methods return array reference, the rest scalars. The addr method is equivalent to the zeroth element in the addr_list array reference.

You may also import all the structure fields directly into your namespace as regular variables using the :FIELDS import tag. (Note that this still overrides your core functions.) Access these fields as variables named with a preceding h_. Thus, $host_obj->name() corresponds to $h_name if you import the fields. Array references are available as regular array variables, so for example @{ $host_obj->aliases() } would be simply @h_aliases.

The gethost() function is a simple front-end that forwards a numeric argument to gethostbyaddr() by way of Socket::inet_aton, and the rest to gethostbyname().

To access this functionality without the core overrides, pass the use an empty import list, and then access function functions with their full qualified names. On the other hand, the built-ins are still available via the CORE:: pseudo-package.

EXAMPLES

 use Net::hostent;
 use Socket;

 @ARGV = ('netscape.com') unless @ARGV;

 for $host ( @ARGV ) {

    unless ($h = gethost($host)) {
	warn "$0: no such host: $host\n";
	next;
    }

    printf "\n%s is %s%s\n", 
	    $host, 
	    lc($h->name) eq lc($host) ? "" : "*really* ",
	    $h->name;

    print "\taliases are ", join(", ", @{$h->aliases}), "\n"
		if @{$h->aliases};     

    if ( @{$h->addr_list} > 1 ) { 
	my $i;
	for $addr ( @{$h->addr_list} ) {
	    printf "\taddr #%d is [%s]\n", $i++, inet_ntoa($addr);
	} 
    } else {
	printf "\taddress is [%s]\n", inet_ntoa($h->addr);
    } 

    if ($h = gethostbyaddr($h->addr)) {
	if (lc($h->name) ne lc($host)) {
	    printf "\tThat addr reverses to host %s!\n", $h->name;
	    $host = $h->name;
	    redo;
	} 
    }
 }

NOTE

While this class is currently implemented using the Class::Struct module to build a struct-like class, you shouldn't rely upon this.

AUTHOR

Tom Christiansen