CVE-2026-40199

Publication date 10 April 2026

Last updated 8 June 2026

Ubuntu priority

Cvss 3 Severity Score

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.

Status

Show unmaintained releases

Package	Ubuntu Release	Status
libnet-cidr-lite-perl	26.04 LTS resolute	Fixed 0.22-2ubuntu0.26.04.1
	25.10 questing	Fixed 0.22-2ubuntu0.25.10.1
	24.04 LTS noble	Fixed 0.22-2ubuntu0.24.04.1
	22.04 LTS jammy	Fixed 0.22-1ubuntu0.1
	20.04 LTS focal	Fixed 0.21-2ubuntu0.1+esm1
	18.04 LTS bionic	Fixed 0.21-1ubuntu0.18.04.1~esm1
	16.04 LTS xenial	Ignored end of ESM support, was needs-triage

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Severity score breakdown

Parameter	Value
Base score	6.5 · Medium
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	Low
Integrity impact	Low
Availability impact	None
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References

Related Ubuntu Security Notices (USN)

USN-8406-1
Net::CIDR::Lite vulnerabilities
8 June 2026