Net::CIDR::Lite versions before 0.23 for Perl mishandles IPv4 mapped IPv6 addresses, which may allow IP ACL bypass
Summary
Net::CIDR::Lite versions before 0.23 for Perl mishandles IPv4 mapped IPv6 addresses, which may allow IP ACL bypass
Original description
The description as published by the source.
Net::CIDR::Lite versions before 0.23 for Perl mishandles IPv4 mapped IPv6 addresses, which may allow IP ACL bypass.
_pack_ipv6() includes the sentinel byte from _pack_ipv4() when building the packed representation of IPv4 mapped addresses like ::ffff:192.168.1.1. This produces an 18 byte value instead of 17 bytes, misaligning the IPv4 part of the address.
The wrong length causes incorrect results in mask operations (bitwise AND truncates to the shorter operand) and in find() / bin_find() which use Perl string comparison (lt/gt). This can cause find() to incorrectly match or miss addresses.
Example:
my $cidr = Net::CIDR::Lite->new("::ffff:192.168.1.0/120");
$cidr->find("::ffff:192.168.2.0"); # incorrectly returns true
This is triggered by valid RFC 4291 IPv4 mapped addresses (::ffff:x.x.x.x).
See also CVE-2026-40198, a related issue in the same function affecting malformed IPv6 addresses.
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Alpine Linux ALPINE-CVE-2026-40199 perl-net-cidr-lite Fixed in: 0.23-r0
- Debian DEBIAN-CVE-2026-40199 libnet-cidr-lite-perl
- Ubuntu UBUNTU-CVE-2026-40199 libnet-cidr-lite-perl
References
- advisory github.com
- advisory metacpan.org
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web cpan.org
- web cve.org