========================================================================
CVE-2026-40199                                       CPAN Security Group
========================================================================

        CVE ID:  CVE-2026-40199
  Distribution:  Net-CIDR-Lite
      Versions:  before 0.23

      MetaCPAN:  https://metacpan.org/dist/Net-CIDR-Lite
      VCS Repo:  https://github.com/stigtsp/Net-CIDR-Lite

Net::CIDR::Lite versions before 0.23 for Perl mishandles IPv4 mapped
IPv6 addresses, which may allow IP ACL bypass

Description
-----------
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.

Problem types
-------------
- CWE-130 Improper Handling of Length Parameter Inconsistency

Solutions
---------
Upgrade to version 0.23 or newer, or apply the patch provided.

References
----------
https://github.com/stigtsp/Net-CIDR-Lite/commit/b7166b1fa17b3b14b4c795ace5b3fbf71a0bd04a.patch
https://metacpan.org/release/STIGTSP/Net-CIDR-Lite-0.23/changes
https://www.cve.org/CVERecord?id=CVE-2026-40198

Timeline
--------
- 2026-04-09: Vulnerability found
- 2026-04-10: Net-CIDR-Lite version 0.23 released