CVE-2018-7685 in libzypp
Summary
by MITRE
The decoupled download and installation steps in libzypp before 17.5.0 could lead to a corrupted RPM being left in the cache, where a later call would not display the corrupted RPM warning and allow installation, a problem caused by malicious warnings only displayed during download.
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Analysis
by VulDB Data Team • 05/06/2023
The vulnerability identified as CVE-2018-7685 resides within the libzypp package management library, which serves as the core component for software package handling in SUSE Linux distributions. This flaw represents a critical security issue that undermines the integrity of the package installation process by exploiting a design weakness in how the library manages download and installation phases. The vulnerability affects versions prior to 17.5.0 and specifically targets the caching mechanism that stores downloaded RPM packages before their installation. The fundamental problem emerges from the decoupled nature of download and installation operations, creating a window where malicious actors can manipulate the system's behavior during package acquisition.
The technical implementation of this vulnerability stems from the library's failure to properly validate package integrity throughout the entire acquisition lifecycle. During the download phase, the system caches RPM packages in a temporary location while simultaneously displaying warnings that are only visible during this initial stage. When malicious actors manipulate the download process, they can inject false warnings that appear only during the retrieval phase, creating a deceptive user experience where legitimate warnings are suppressed or altered. This design flaw allows attackers to bypass security checks that would normally prevent installation of corrupted or malicious packages, as the system's warning mechanisms are selectively disabled during the critical installation phase. The vulnerability specifically affects the caching subsystem where downloaded packages are stored, potentially leaving corrupted RPM files in the cache directory where they can be silently installed without proper integrity verification.
The operational impact of this vulnerability extends beyond simple package management failures, creating a significant attack surface that could enable privilege escalation and system compromise. Attackers can exploit this weakness by injecting malicious packages during download operations, where the false warnings during acquisition would mislead administrators into believing the packages are legitimate. The system's inability to properly warn about corrupted packages during the installation phase creates a false sense of security, allowing malicious software to be silently installed on target systems. This vulnerability directly violates security principles of least privilege and defense in depth, as it allows attackers to bypass multiple layers of protection that should normally prevent the installation of compromised packages. The issue also creates potential for supply chain attacks where attackers can manipulate package repositories to deliver malicious content that appears legitimate during download but becomes active during installation.
Mitigation strategies for CVE-2018-7685 require immediate patching of affected libzypp versions to 17.5.0 or later, which implements proper integrity validation throughout the download and installation lifecycle. Organizations should also implement additional verification measures including checksum validation of downloaded packages, monitoring of cache directories for suspicious file modifications, and regular security auditing of package management systems. The fix addresses the core issue by ensuring that warning mechanisms remain active throughout the entire package acquisition process, preventing the selective disabling of security alerts that enabled the attack vector. System administrators should also consider implementing network-level controls to prevent unauthorized package modifications and establish proper access controls around package repositories. This vulnerability aligns with CWE-229, which addresses weaknesses in the handling of externally-supplied data in package management systems, and maps to ATT&CK technique T1059.007 for package management trojans that exploit software supply chain vulnerabilities. The remediation process must include comprehensive testing of package management workflows to ensure that the patched version properly handles all package states and maintains consistent security validation across download and installation phases.