# CVE-2026-40198: libnet-cidr-lite-perl: Net::CIDR::Lite versions before 0.23 for Perl does not validate IPv6 group count, which may allow IP ACL bypass

CVE-2026-40198 is fixed in 2 products on 1 platform, first by libnet-cidr-lite-perl 0.21-1ubuntu0.18.04.1~esm1, released April 10, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-40198
- Priority: High
- CVSS: 7.5 (high)
- EPSS: 0.0032
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Apr 10, 2026

## Description

Net::CIDR::Lite versions before 0.23 for Perl does not validate IPv6 group count, which may allow IP ACL bypass.  _pack_ipv6() does not check that uncompressed IPv6 addresses (without ::) have exactly 8 hex groups. Inputs like "abcd", "1:2:3", or "1:2:3:4:5:6:7" are accepted and produce packed values of wrong length (3, 7, or 15 bytes instead of 17).  The packed values are used internally for mask and comparison operations. find() and bin_find() use Perl string comparison (lt/gt) on these values, and comparing strings of different lengths gives wrong results. This can cause find() to incorrectly report an address as inside or outside a range.  Example:    my $cidr = Net::CIDR::Lite->new("::/8");   $cidr->find("1:2:3");  # invalid input, incorrectly returns true  This is the same class of input validation issue as CVE-2021-47154 (IPv4 leading zeros) previously fixed in this module.  See also CVE-2026-40199, a related issue in the same function affecting IPv4 mapped IPv6 addresses.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libnet-cidr-lite-perl Debian 12.15 (bookworm) | 0.22-3~deb12u1 | [DEBIAN-CVE-2026-40198](https://patchblox.com/security/data/fix/linux/debian-cve-2026-40198.md) | Apr 10, 2026 |
| Linux | libnet-cidr-lite-perl Debian 13.5 (trixie) | 0.22-3~deb13u1 | [DEBIAN-CVE-2026-40198](https://patchblox.com/security/data/fix/linux/debian-cve-2026-40198.md) | Apr 10, 2026 |
| Linux | libnet-cidr-lite-perl Debian 14 | 0.22-3 | [DEBIAN-CVE-2026-40198](https://patchblox.com/security/data/fix/linux/debian-cve-2026-40198.md) | Apr 10, 2026 |
| Linux | libnet-cidr-lite-perl Ubuntu 18.04.6 LTS (bionic) | 0.21-1ubuntu0.18.04.1~esm1 | [libnet-cidr-lite-perl 0.21-1ubuntu0.18.04.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libnet-cidr-lite-perl-0.21-1ubuntu0.18.04.1-esm1.md) | Apr 10, 2026 |
| Linux | libnet-cidr-lite-perl Ubuntu 20.04 LTS (focal) | 0.21-2ubuntu0.1+esm1 | [libnet-cidr-lite-perl 0.21-2ubuntu0.1+esm1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libnet-cidr-lite-perl-0.21-2ubuntu0.1-esm1.md) | Apr 10, 2026 |
| Linux | libnet-cidr-lite-perl Ubuntu 22.04.1 LTS (jammy) | 0.22-1ubuntu0.1 | [libnet-cidr-lite-perl 0.22-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-libnet-cidr-lite-perl-0.22-1ubuntu0.1.md) | Apr 10, 2026 |
| Linux | libnet-cidr-lite-perl Ubuntu 24.04.5 LTS (noble) | 0.22-2ubuntu0.24.04.1 | [libnet-cidr-lite-perl 0.22-2ubuntu0.24.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-libnet-cidr-lite-perl-0.22-2ubuntu0.24.04.1.md) | Apr 10, 2026 |
| Linux | libnet-cidr-lite-perl Ubuntu 25.10 (questing) | 0.22-2ubuntu0.25.10.1 | [libnet-cidr-lite-perl 0.22-2ubuntu0.25.10.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-libnet-cidr-lite-perl-0.22-2ubuntu0.25.10.1.md) | Apr 10, 2026 |
| Linux | libnet-cidr-lite-perl Ubuntu 26.04.1 LTS (resolute) | 0.22-2ubuntu0.26.04.1 | [libnet-cidr-lite-perl 0.22-2ubuntu0.26.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libnet-cidr-lite-perl-0.22-2ubuntu0.26.04.1.md) | Apr 10, 2026 |
| Linux | perl-Net-CIDR-Lite amzn 2023 | 0.22-8.amzn2023.0.1 | [ALAS2023-2026-1624](https://patchblox.com/security/data/fix/linux/alas2023-2026-1624.md) | Apr 27, 2026 |

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