CVE-2026-40199
MEDIUMDescription
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.
How to fix
This Ubuntu release reached end-of-life on 2023-05-31. Extended security maintenance is available until 2028-04-01.
This Ubuntu release reached end-of-life on 2025-05-31. Extended security maintenance is available until 2030-04-02.
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 23% of all known CVEs.
References
Related Vulnerabilities
Other CWE-130 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2025-14847 | High | 7.5 | 83% | KEV | Fix |
| CVE-2024-39614 | High | 7.5 | 29% | - | Fix |
| CVE-2021-36090 | High | 7.5 | 13% | - | Fix |
| CVE-2021-35516 | High | 7.5 | 12% | - | Fix |
| CVE-2021-35517 | High | 7.5 | 11% | - | Fix |
| CVE-2019-3862 | High | 7.3 | 8.1% | - | Fix |
Common questions
How do I fix CVE-2026-40199?
Published advisories record a fix for 3 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-40199 being actively exploited?
Not that we know of. CVE-2026-40199 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.31% is the estimated probability that it will be exploited in the next 30 days. That is higher than 23% of all scored CVEs.
How severe is CVE-2026-40199?
CVE-2026-40199 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-40199 affect?
Published advisories record a fix for perl-Net-CIDR-Lite (Amazon), libnet-cidr-lite-perl (Debian), libnet-cidr-lite-perl (Ubuntu). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-06-17.