🛡️ CVE-2026-40199 — net\

🟡 CVSS 6.5 — Medium ✅ No Known Exploit CWE-130 NVD
6.5
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality low, integrity low, availability none.

Affected software

CVE-2026-40199 is recorded against 1 package.

  • net\ (fixed in 0.23)

Timeline and source

Published on 10 April 2026 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
metacpan.org
www.cve.org

CVE-2026-40199 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity MEDIUM
CVSS Score 6.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
CWE CWE-130
Public Exploit ✅ No
Source NVD
Published 2026-04-10
Updated 2026-08-11
Modified 2026-06-17

Affected Packages

Software From version Fixed in
net\ — 0.23

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