IP ACL bypass via malformed IPv6 groups
Published Apr 10, 2026 · Updated Apr 10, 2026
Improper IPv6 validation in Net::CIDR::Lite before 0.23 allows remote attackers to bypass IP access controls with malformed addresses. _pack_ipv6() accepts uncompressed IPv6 input without requiring eight hex groups, producing short packed strings that find() and bin_find() compare lexically. Exploitation requires a consuming application to pass attacker-controlled addresses into membership checks, causing false allow or deny results rather than code execution.
Summary
What happened
Improper IPv6 validation in Net::CIDR::Lite before 0.23 allows remote attackers to bypass IP access controls with malformed addresses. _pack_ipv6() accepts uncompressed IPv6 input without requiring eight hex groups, producing short packed strings that find() and bin_find() compare lexically. Exploitation requires a consuming application to pass attacker-controlled addresses into membership checks, causing false allow or deny results rather than code execution.
The record
- CVE
- CVE-2026-40198
- Published
- Apr 10, 2026
- Updated
- Apr 10, 2026
- Vendor
- Stig Palmquist
- Product
- Net::CIDR::Lite
- Classifications
- CWE-1286
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 10, 2026CVE publishedPublication date reported by the CVE source.
- Apr 10, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <0.23
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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