CVE-2026-40199
MediumCVSS 6.5Exploitation Probability (EPSS)
Low risk23th percentile - higher than 23% of all known CVEs
Summary
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(), producing an 18-byte value instead of 17 bytes, causing incorrect results in mask operations and in find()/bin_find().
Risk Assessment
This may lead to incorrect address matching in ACLs, enabling bypass of IP access controls. Organizations relying on Net::CIDR::Lite for address filtering are exposed.
Recommendation
Upgrade Net::CIDR::Lite to version 0.23 or later. Until updated, avoid relying on this library for ACLs with IPv4 mapped IPv6 addresses.
Other vulnerabilities in Net::CIDR::Lite
See all- CVE-2026-45191Medium
In Net::CIDR::Lite for Perl (versions before 0.24), extraneous zero characters in CIDR mask values are not properly considered, which may allow IP ACL bypass. Masks like "/00" and "/01" pass validation and parse to the same prefix as their unpadded value.
- CVE-2026-45190Medium
Net::CIDR::Lite for Perl before version 0.24 does not properly validate IP address and CIDR mask inputs, which may allow IP ACL bypass. Inputs with trailing newline or non-ASCII digit characters pass validators but are re-encoded to a different address, causing incorrect matches.
Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS