Net::CIDR::Lite Flaws Enable IP Access Control Bypass Attacks
Two critical vulnerabilities in the Net::CIDR::Lite Perl library allow attackers to bypass IP-based access control lists through improper input validation. Ubuntu has released security updates to address these issues affecting systems relying on CIDR notation for network access policies.
TL;DR
- Net::CIDR::Lite contains two CVEs (CVE-2026-45190, CVE-2026-45191) that enable IP access control list bypass
- Flawed IP address and CIDR mask validation allows attackers to circumvent network-level security controls
- Extraneous zero characters in CIDR masks can be exploited to evade filtering rules
- Ubuntu security update USN-8453-1 patches both vulnerabilities in affected systems
- Organizations using CIDR-based access controls should prioritize patching to prevent unauthorized access
Net::CIDR::Lite, a widely-used Perl library for handling Classless Inter-Domain Routing (CIDR) notation, contains two validation flaws that could allow attackers to circumvent IP-based access control lists. These vulnerabilities stem from improper handling of IP address inputs and CIDR mask formatting, creating a potential security gap in network access policies that rely on this library.
The first vulnerability involves inadequate validation of IP addresses and CIDR masks, while the second specifically targets how the library processes extraneous zero characters within mask values. Both issues could be exploited by attackers to craft malicious inputs that bypass filtering rules designed to restrict network access.
Ubuntu has addressed these issues through security update USN-8453-1, which patches both CVE-2026-45190 and CVE-2026-45191. Organizations using Net::CIDR::Lite in production environments should apply these updates promptly to restore the integrity of their network access controls.
Vulnerability Details and Attack Vectors
- CVE-2026-45190 exploits insufficient validation of IP address and CIDR mask inputs to bypass access control lists
- CVE-2026-45191 abuses improper handling of leading zeros in CIDR mask values to evade filtering rules
- Both vulnerabilities allow attackers to craft inputs that pass validation checks while violating intended access policies
- The flaws affect any system using Net::CIDR::Lite for network-level security decisions
Impact and Remediation
- Unauthorized network access could result from successful exploitation of these validation bypasses
- Systems relying on CIDR notation for firewall rules, VPN access controls, or API rate limiting are at risk
- Ubuntu security update USN-8453-1 provides patched versions of the affected library
- Administrators should apply patches immediately and verify that access control policies remain effective after updates
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