CVE-2020-16155 in CPAN::Checksums
Summary
by MITRE • 12/13/2021
The CPAN::Checksums package 2.12 for Perl does not uniquely define signed data.
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 12/16/2021
The CPAN::Checksums package version 2.12 for Perl contains a critical vulnerability that undermines the integrity verification mechanism designed to protect software distribution channels. This vulnerability stems from the package's failure to properly define the signed data structure, which creates opportunities for attackers to manipulate checksums without detection. The flaw exists within the cryptographic signing process that should ensure the authenticity and integrity of Perl module distributions downloaded from the Comprehensive Perl Archive Network. When developers or users rely on checksum verification to confirm that downloaded packages have not been tampered with, this vulnerability effectively renders that security measure ineffective.
The technical root cause of CVE-2020-16155 lies in the improper handling of data serialization within the CPAN::Checksums module. Specifically, the package does not consistently define the exact data elements that should be included in the cryptographic signature process. This ambiguity allows attackers to craft modified package distributions that will pass checksum verification despite containing malicious code. The vulnerability manifests when the signing and verification processes use different data representations, creating a mismatch that enables attackers to bypass security checks. This issue directly relates to CWE-347, which addresses improper verification of cryptographic signatures, and aligns with ATT&CK technique T1553.006 for bypassing security measures through signature validation manipulation.
The operational impact of this vulnerability extends beyond simple checksum validation failures, potentially enabling supply chain attacks against Perl development environments. Attackers could exploit this weakness to inject malicious code into legitimate-looking Perl modules, which would then be downloaded and installed by unsuspecting developers. This creates a significant risk for organizations that rely on Perl-based applications and automated deployment pipelines. The vulnerability affects the entire CPAN ecosystem, as the checksums are used to verify the integrity of modules distributed across multiple repositories and mirrors. Security tools and automated systems that depend on CPAN::Checksums for package validation would fail to detect compromised packages, leading to potential system compromise through malicious code execution.
Organizations should immediately update to CPAN::Checksums version 2.13 or later, which contains the necessary fixes to properly define the signed data structure. System administrators should also implement additional verification measures such as manual checksum validation, code review processes, and monitoring for anomalous package installations. Security teams should consider implementing network-based detection measures to identify potential exploitation attempts through unusual package download patterns. The fix addresses the core issue by establishing consistent data serialization rules for cryptographic signing and verification, ensuring that the same data elements are processed during both signing and verification phases. This remediation aligns with best practices outlined in NIST SP 800-53 for cryptographic module security requirements and helps prevent the exploitation patterns described in the MITRE ATT&CK framework's software supply chain compromise techniques.