CVE-2026-40198 Net::CIDR::Lite versions before 0.23 for Perl does not validate IPv6 group count, which may allow IP ACL bypass
Attackers can bypass IP-based access controls by providing malformed IPv6 addresses that cause incorrect range matching in the Net::CIDR::Lite Perl library.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-40198?
CVE-2026-40198 is a high-severity vulnerability in STIGTSP Net::CIDR::Lite, published on 10 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-1286
Which versions are affected by CVE-2026-40198?
It affects 1 product.
Products include Stigtsp Net\.
How do I fix CVE-2026-40198?
Upgrade to a fixed version.
Is CVE-2026-40198 being exploited?
There is no known exploitation of CVE-2026-40198 in the wild and no public exploit code.
Other vulnerabilities in STIGTSP Net::CIDR::Lite
Sources
Also known as ALPINE-CVE-2026-40198, AZL-82739, DEBIAN-CVE-2026-40198, GHSA-c25q-mqx5-m6v8, UBUNTU-CVE-2026-40198.