CVE-2026-40198
CWE-1286Published: April 10, 2026· Updated: Apr 13, 2026
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.
Technical Analysis
CVE-2026-40198 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.
A successful exploit results in full integrity compromise (data manipulation), with a CVSS base score of 7.5.
A proof-of-concept (PoC) exploit exists for CVE-2026-40198. While not yet confirmed in active campaigns, the availability of PoC code increases exploitation risk substantially.
CVSS v3.1 Vector Breakdown
Exploit & PoC Resources
All References (3)
Quick Facts
Related CVEs (CWE-1286)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-40198 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts