CVE-2026-40198: Net::CIDR::Lite versions before 0.23 for Perl does not validate IPv6 group count, which may allow IP ACL bypas

Q: How do I fix CVE-2026-40198?

net\: upgrade to 0.23. Exact commands for each OS are on this page.

Q: Is CVE-2026-40198 being exploited?

CVE-2026-40198 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-40198 affect?

CVE-2026-40198 affects net\. Severity is high (CVSS 7.5). 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:

Q: How urgent is CVE-2026-40198?

Priority 37/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.5REMOTEUPGRADE

CVE-2026-40198 is a high-severity flaw (CVSS 7.5) affecting net\. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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()

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 76%)
CISA exploited list	No
Weakness	CWE-1286
Published	2026-04-10
Last modified	2026-10-26

Publisher (CNA): CPANSec · Vendor: stigtsp

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-10 22:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

stigtsp net\ UPGRADE

Affected: < 0.23

Fixed in: 0.23

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy net || rpm -q net || net --version

2. UPGRADE to 0.23 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade net

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade net

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-40198?

net\: upgrade to 0.23. Exact commands for each OS are on this page.

Is CVE-2026-40198 being exploited?

CVE-2026-40198 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-40198 affect?

CVE-2026-40198 affects net\. Severity is high (CVSS 7.5). 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:

How urgent is CVE-2026-40198?

Priority 37/100. High severity; Remotely exploitable, no login, no user action

Software pages

Perl vulnerabilities

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References

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