CVE-2015-3407 in Module::Signature
Summary
by MITRE
Module::Signature before 0.74 allows remote attackers to bypass signature verification for files via a signature file that does not list the files.
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Analysis
by VulDB Data Team • 05/18/2022
The vulnerability identified as CVE-2015-3407 affects Module::Signature version 0.74 and earlier, representing a critical flaw in the Perl module signature verification mechanism. This issue resides in the cryptographic verification process used to ensure the integrity and authenticity of Perl modules distributed through the Comprehensive Perl Archive Network. The vulnerability stems from a design flaw in how signature files are processed and validated, creating a potential attack vector for malicious actors seeking to compromise the security of Perl module installations.
The technical flaw occurs when Module::Signature processes signature files that contain entries for files that are not actually present in the corresponding module distribution. This discrepancy allows attackers to craft malicious signature files that appear valid to the verification system while actually covering files that were never included in the legitimate module package. The vulnerability specifically exploits the verification logic that fails to properly validate whether all files referenced in a signature file are actually part of the module being verified, creating a bypass mechanism for signature validation. This represents a weakness in the cryptographic validation process that should ensure all claimed files are present and properly signed.
The operational impact of this vulnerability is significant for systems relying on Perl module security through signature verification. Attackers can exploit this flaw to install malicious code within legitimate-looking module distributions, potentially compromising entire systems where these modules are installed. The vulnerability affects the fundamental security model of Perl module distribution, as it undermines the trust model that depends on cryptographic signatures to verify module integrity. Systems using older versions of Module::Signature are particularly vulnerable because the verification process does not properly enforce the requirement that all files mentioned in a signature must actually exist in the module package. This creates a scenario where attackers can manipulate the verification process to allow installation of modified or malicious code.
The vulnerability aligns with CWE-347, which addresses improper validation of cryptographic signatures, and represents a failure in proper input validation and cryptographic verification processes. From an ATT&CK framework perspective, this vulnerability could be leveraged in the execution phase of an attack, specifically through the use of malicious code injection techniques where attackers manipulate the module verification process to bypass security controls. Organizations using Perl-based systems should prioritize updating to Module::Signature version 0.74 or later, as this release includes fixes for the signature validation logic. Additional mitigation strategies include implementing additional verification layers, monitoring module installations for suspicious activity, and considering alternative package management approaches that provide stronger integrity guarantees. The vulnerability also highlights the importance of proper cryptographic validation in software distribution systems and demonstrates how seemingly minor flaws in signature verification can have major security implications for entire ecosystems.