CVE-2014-6278 in Bash
Summary
by MITRE
GNU Bash through 4.3 bash43-026 does not properly parse function definitions in the values of environment variables, which allows remote attackers to execute arbitrary commands via a crafted environment, as demonstrated by vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, scripts executed by unspecified DHCP clients, and other situations in which setting the environment occurs across a privilege boundary from Bash execution. NOTE: this vulnerability exists because of an incomplete fix for CVE-2014-6271, CVE-2014-7169, and CVE-2014-6277.
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Analysis
by VulDB Data Team • 04/22/2026
The vulnerability described in CVE-2014-6278 represents a critical security flaw in GNU Bash that emerged from an incomplete remediation of previously discovered vulnerabilities. This issue affects Bash versions through 4.3 bash43-026 and stems from improper parsing of function definitions within environment variable values, creating a fundamental weakness in how the shell processes environment data. The vulnerability specifically exploits the manner in which Bash handles environment variables containing function definitions, allowing attackers to inject malicious code that executes when the shell processes these variables. This flaw operates at the core of Bash's environment handling mechanisms, making it particularly dangerous as it can be triggered through multiple attack vectors across different systems and applications.
The technical implementation of this vulnerability occurs when Bash encounters environment variables that contain function definitions with specific formatting patterns. When these variables are processed, the shell incorrectly interprets the function definitions as executable commands rather than mere definitions, leading to arbitrary code execution. The exploitation mechanism relies on the fact that Bash allows function definitions to be embedded within environment variable values, and when these values are processed, the shell's parsing logic fails to properly sanitize or isolate the function definition portion from the command execution portion. This parsing error creates a code injection opportunity where malicious payloads can be executed with the privileges of the affected process, often resulting in full system compromise.
The operational impact of CVE-2014-6278 extends far beyond a single application or service, as it affects numerous systems that rely on Bash for command execution. The vulnerability demonstrates particular severity when exploited through the ForceCommand feature in OpenSSH sshd, where remote attackers can inject commands that execute with the privileges of the SSH session. Additionally, the flaw impacts Apache HTTP Server modules mod_cgi and mod_cgid, allowing attackers to execute arbitrary code through CGI scripts, and affects DHCP clients that process environment variables during network configuration. This broad attack surface means that systems using Bash across privilege boundaries are at risk, with potential exploitation occurring in scenarios where environment variables are set by untrusted sources and subsequently processed by Bash. The vulnerability creates a persistent threat vector that can be leveraged for privilege escalation, data exfiltration, and complete system compromise.
The remediation strategy for CVE-2014-6278 requires immediate patching of affected Bash versions with the appropriate security updates that properly address the parsing flaw. Organizations should implement comprehensive vulnerability scanning to identify all systems running affected Bash versions and prioritize patching across all environments. Network segmentation and privilege separation measures should be enhanced to limit the potential impact of successful exploitation, while monitoring systems should be deployed to detect anomalous command execution patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-78 and CWE-79 categories related to command injection and improper input validation, and maps to ATT&CK techniques involving privilege escalation and command execution through environment manipulation. Regular security audits and vulnerability assessments should be conducted to ensure that similar parsing flaws are not present in other system components that may be vulnerable to similar injection attacks.