Subject: Mitigating CVE- 2014-7187: “Shellshock” or “Bash Bug” Vulnerability
TECH STACK: GNU BASH – All Unix Operating Systems
DATE(S) ISSUED: 09/28/2014
NVD Last Modified: 10/09/2018
CRITICALITY: 10 Critical
- Broad Impact: The issue affects not just websites but any system that run Bash scripts.
- How It Works: Hackers can use unsafe user input to trick systems into running harmful commands.
- Exploitation: Malicious cookies or stored user data can be used to take control of web servers.
- Detected Threats: Attackers have used this vulnerability to install remote access tools, open backdoors, and upload harmful files such as ransomware.
- Immediate Action: Apply software updates to prevent attacks.
OVERVIEW:
This document outlines the steps to mitigate the vulnerability (CVE- 2014-7187), which affects versions 1.14 through 4.3. This vulnerability allows a remote attacker to execute arbitrary commands on the system, caused by an error when evaluating specially crafted environment variables passed to it by the bash functionality. An attacker could exploit this vulnerability to write to files and execute arbitrary commands on the system.
SOLUTION/MITIGATION:
- Upgrade Bash: Update the Bash shell to a non-vulnerable version. Check with your operating system vendor or software provider for the latest patched version of Bash and upgrade accordingly.
- Apply Operating System patches and updates (if necessary): It is crucial to apply the latest security patches and updates provided by operating system vendors and software developers. These patches address the Shellshock vulnerability and help protect systems from potential exploitation. Regularly check for updates and ensure they are promptly applied.
- Restrict access to bash: Limit access to the Bash shell, particularly in cases where it is not required.
- Disable or restrict shell access for user accounts that do not need it, reducing the attack surface and potential avenues for exploitation.
Additional mitigation steps:
- Web server configuration: When running a web server, configure it to sanitize and validate user-supplied input. Web applications and CGI scripts should be reviewed and modified to ensure they are not susceptible to Shellshock attacks.
- Network device hardening: For network devices that use Bash or Bash-based tools, ensure they are running the latest patched versions. Follow security best practices for network device hardening, including using strong passwords, disabling unnecessary services, and regularly updating firmware.
- Regular security audits: Conduct regular security audits and vulnerability assessments to identify potential weaknesses in systems and applications. Use automated scanning tools or engage third-party security professionals to assess the security posture of your infrastructure. By implementing these precautions and mitigation measures, organizations can significantly reduce the risk of exploitation and protect their systems from the Shellshock vulnerability.
Confirmation & Additional Information:
- Verify that the mitigation steps have been successfully implemented.
- Keep your Bash and Operating Systems up-to-date with the latest security patches.
- Refer to the following resources for additional information: https://nvd.nist.gov/vuln/detail/CVE-2014-7187
Related CVES: VE-2014-6271, CVE-2014-7169, CVE-2014-7186, CVE-2014-6277, CVE-2014-6278
This document is provided for informational purposes only and should not be considered a substitute for professional security advice.
