CVE-2026-40199 Affecting libnet-cidr-lite-perl package, versions <0.22-3


Severity

Recommended
low

Based on default assessment until relevant scores are available.

Threat Intelligence

EPSS
0.31% (24th percentile)

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  • Snyk IDSNYK-DEBIANUNSTABLE-LIBNETCIDRLITEPERL-16031117
  • published14 Apr 2026
  • disclosed10 Apr 2026

Introduced: 10 Apr 2026

CVE-2026-40199  (opens in a new tab)

How to fix?

Upgrade Debian:unstable libnet-cidr-lite-perl to version 0.22-3 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream libnet-cidr-lite-perl package and not the libnet-cidr-lite-perl package as distributed by Debian. See How to fix? for Debian:unstable relevant fixed versions and status.

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.

CVSS Base Scores

version 3.1