CVE-2019-18276 Explained : Impact and Mitigation

A vulnerability has been identified in the disable_priv_mode function within the shell.c file of GNU Bash up to version 5.0 patch 11. This vulnerability allows an attacker to execute commands within the shell and potentially regain privileges.

Understanding CVE-2019-18276

This CVE involves a privilege escalation vulnerability in GNU Bash up to version 5.0 patch 11.

What is CVE-2019-18276?

CVE-2019-18276 is a security flaw in GNU Bash that mishandles the dropping of privileges when the effective UID is different from the real UID, potentially allowing an attacker to execute arbitrary commands and regain privileges.

The Impact of CVE-2019-18276

The vulnerability in GNU Bash up to version 5.0 patch 11 can be exploited by an attacker to execute commands within the shell and load a new built-in function at runtime, potentially leading to privilege escalation.

Technical Details of CVE-2019-18276

This section provides detailed technical information about the vulnerability.

Vulnerability Description

The disable_priv_mode function in shell.c in GNU Bash through 5.0 patch 11 incorrectly handles dropping privileges, allowing an attacker to regain privileges by loading a new built-in function at runtime.

Affected Systems and Versions

GNU Bash up to version 5.0 patch 11

Exploitation Mechanism

Attackers can exploit this vulnerability by executing commands within the shell and using the "enable -f" command to load a new built-in function that calls setuid(), enabling privilege escalation.

Mitigation and Prevention

Protecting systems from CVE-2019-18276 requires immediate action and long-term security practices.

Immediate Steps to Take

Update GNU Bash to a patched version that addresses the vulnerability.
Monitor system logs for any suspicious activities that could indicate exploitation.

Long-Term Security Practices

Implement the principle of least privilege to restrict user permissions.
Regularly audit and review shell scripts and functions for potential security risks.

Patching and Updates

Apply security patches provided by GNU Bash to mitigate the vulnerability and prevent exploitation.