CVE-2021-32556 in Apport
Summary
by MITRE • 06/12/2021
It was discovered that the get_modified_conffiles() function in backends/packaging-apt-dpkg.py allowed injecting modified package names in a manner that would confuse the dpkg(1) call.
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Analysis
by VulDB Data Team • 06/14/2021
The vulnerability identified as CVE-2021-32556 resides within the get_modified_conffiles() function located in the backends/packaging-apt-dpkg.py file of a software package management system. This flaw represents a classic command injection vulnerability that occurs when user-supplied input is not properly sanitized before being incorporated into system commands. The function processes package names and configuration file modifications during package management operations, creating a pathway for malicious input to influence the execution flow of dpkg commands through improper input validation mechanisms.
The technical exploitation of this vulnerability stems from inadequate input sanitization within the packaging backend component that handles apt and dpkg operations. When the get_modified_conffiles() function processes package names, it fails to properly escape or validate special characters that could be interpreted by the underlying dpkg command processor. This allows attackers to inject malicious package names that contain shell metacharacters or command separators, effectively enabling arbitrary command execution within the context of the package management system. The vulnerability directly maps to CWE-78, which describes improper neutralization of special elements used in OS commands, and CWE-94, which covers improper control of generation of code.
The operational impact of this vulnerability extends beyond simple command injection, as it can enable attackers to manipulate package installations, modify system configurations, or potentially escalate privileges within the affected environment. An attacker who successfully exploits this vulnerability could modify package contents, install malicious software, or disrupt normal system operations through the package management framework. The issue particularly affects systems that rely on dpkg for package management and are vulnerable to manipulation of configuration file processing during package operations. The ATT&CK framework categorizes this vulnerability under T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation, as the vulnerability can be leveraged to execute arbitrary code with elevated privileges.
Mitigation strategies for CVE-2021-32556 should focus on implementing proper input validation and sanitization within the get_modified_conffiles() function. The most effective approach involves escaping special characters in package names before passing them to dpkg commands, using parameterized command execution where possible, and implementing strict validation of input formats. Organizations should also consider applying the vendor-provided patches or updates that address this specific vulnerability. Additionally, implementing network segmentation and privilege separation can reduce the potential impact of successful exploitation, while monitoring systems should be configured to detect anomalous package management activities that might indicate exploitation attempts. The fix should ensure that package names are properly quoted or escaped to prevent shell interpretation of special characters, aligning with secure coding practices recommended by the Open Web Application Security Project and other cybersecurity frameworks.