CVE-2014-1927 in python-gnupg
Summary
by MITRE
The shell_quote function in python-gnupg 0.3.5 does not properly quote strings, which allows context-dependent attackers to execute arbitrary code via shell metacharacters in unspecified vectors, as demonstrated using "$(" command-substitution sequences, a different vulnerability than CVE-2014-1928. NOTE: this vulnerability exists because of an incomplete fix for CVE-2013-7323.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 04/03/2022
The vulnerability identified as CVE-2014-1927 resides within the python-gnupg library version 0.3.5, specifically within the shell_quote function implementation. This flaw represents a critical security issue that enables context-dependent attackers to execute arbitrary code through improper string quoting mechanisms. The vulnerability manifests when shell metacharacters are present in input strings that undergo processing by the affected function, creating a pathway for command injection attacks. The issue is particularly concerning because it demonstrates a regression in security measures, as it stems from an incomplete fix for a previously identified vulnerability CVE-2013-7323, indicating a pattern of flawed remediation efforts that leave systems vulnerable to exploitation.
The technical implementation of the shell_quote function fails to adequately sanitize input strings before they are passed to shell execution contexts. When command substitution sequences such as "$(" are present in the input, the function does not properly escape or quote these special characters, allowing them to be interpreted by the underlying shell as executable commands rather than literal string data. This represents a classic command injection vulnerability that operates under CWE-78, which specifically addresses improper neutralization of special elements used in OS commands. The vulnerability is particularly dangerous because it operates in a context-dependent manner, meaning that the attack vector is not immediately obvious and requires specific conditions to be met for exploitation to occur successfully.
From an operational perspective, this vulnerability creates significant risk for systems that rely on python-gnupg for cryptographic operations involving GPG key management and message encryption. Attackers can exploit this flaw by crafting malicious input strings that contain shell metacharacters, which when processed through the vulnerable shell_quote function, result in unauthorized command execution on the target system. The impact extends beyond simple code execution to potentially allow full system compromise, privilege escalation, and data exfiltration. This vulnerability aligns with ATT&CK technique T1059.001 for command and scripting interpreter, as it enables adversaries to execute arbitrary commands through shell injection methods. The fact that this vulnerability exists due to an incomplete fix for CVE-2013-7323 demonstrates the importance of thorough vulnerability remediation and the potential for regression issues that can re-introduce security flaws.
Mitigation strategies for CVE-2014-1927 should prioritize immediate upgrade to a patched version of python-gnupg where the shell_quote function has been properly implemented with comprehensive input sanitization. Organizations should implement additional defensive measures including input validation at multiple layers, restricting shell access for applications using the library, and monitoring for suspicious command execution patterns. The vulnerability also highlights the need for comprehensive security testing including fuzzing and code review processes to identify incomplete fixes and regression issues. System administrators should conduct thorough vulnerability assessments to identify all systems using affected versions of python-gnupg and ensure that proper patch management procedures are in place to prevent similar issues from reoccurring in other software components. The remediation process should include not just updating the library but also reviewing all code that interfaces with GPG functionality to ensure no other similar vulnerabilities exist within the application ecosystem.