CVE-2007-4739 in reprepro
Summary
by MITRE
reprepro 1.3.0 through 2.2.3 does not properly verify signatures when updating repositories, which allows remote attackers to construct and distribute an ostensibly valid Release.gpg file by signing it with an unknown key, related to the update command.
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Analysis
by VulDB Data Team • 07/29/2019
The vulnerability identified as CVE-2007-4739 affects reprepro versions 1.3.0 through 2.2.3, presenting a critical security flaw in repository management systems. This issue specifically impacts the signature verification process during repository updates, creating a pathway for malicious actors to compromise package repositories. The flaw resides in the update command's inability to properly validate cryptographic signatures, allowing attackers to forge valid-looking Release.gpg files that appear authentic to systems relying on standard verification procedures.
The technical nature of this vulnerability stems from insufficient signature validation mechanisms within reprepro's repository update functionality. When administrators use the update command to manage package repositories, the software fails to verify that incoming signatures are associated with trusted keys from the repository's keyring. Attackers can exploit this by generating their own cryptographic keys and signing malicious Release.gpg files, which the vulnerable software will accept as legitimate due to the weak verification process. This represents a fundamental breakdown in the cryptographic integrity checks that should protect package repositories from unauthorized modifications.
The operational impact of CVE-2007-4739 is severe and far-reaching within software distribution ecosystems. Organizations relying on reprepro for managing debian package repositories become vulnerable to supply chain attacks where malicious packages can be injected into trusted environments. When attackers successfully compromise a repository, they can distribute malicious software updates that appear to come from legitimate sources, potentially affecting thousands of systems that trust the compromised repository. The vulnerability undermines the core security assumptions of package management systems, as it allows attackers to bypass the cryptographic protections designed to prevent unauthorized modifications to repository contents.
This vulnerability aligns with CWE-310, which addresses cryptographic issues in software implementations, specifically focusing on signature verification weaknesses. The flaw also maps to ATT&CK technique T1583.001, which covers the development of software tools for supply chain attacks, as attackers can leverage this vulnerability to create convincing malicious repository signatures. Organizations using affected reprepro versions face significant risk of compromise, as the vulnerability operates at the repository level where attackers can manipulate package metadata and distribution files without detection.
Mitigation strategies should prioritize immediate upgrade to reprepro versions that address this signature verification weakness, typically those beyond 2.2.3. System administrators should also implement additional verification measures such as manual key verification before accepting repository updates, implementing repository mirroring with multiple verification points, and establishing robust monitoring for unauthorized repository modifications. Organizations should conduct thorough security audits of their package management infrastructure and consider implementing automated signature validation checks that go beyond the default reprepro verification mechanisms. The vulnerability underscores the critical importance of maintaining up-to-date security software and implementing defense-in-depth strategies for package repository management.