CVE-2021-45444 : Exploit Details and Defense Strategies

In zsh before version 5.8.1, an attacker could execute code by controlling command output within the prompt due to a vulnerability in recursive PROMPT_SUBST expansion.

Understanding CVE-2021-45444

What is CVE-2021-45444?

In zsh before version 5.8.1, an attacker can achieve code execution if they control a command output inside the prompt, as demonstrated by a %F argument. This occurs due to recursive PROMPT_SUBST expansion.

The Impact of CVE-2021-45444

The vulnerability allows an attacker to execute arbitrary code by manipulating the prompt and its expansion mechanism.

Technical Details of CVE-2021-45444

Vulnerability Description

The vulnerability in zsh before 5.8.1 allows attackers to execute code through prompt manipulation with the %F argument due to recursive PROMPT_SUBST expansion.

Affected Systems and Versions

Systems running zsh before version 5.8.1

Exploitation Mechanism

Attackers can exploit this vulnerability by controlling the command output within the prompt, leveraging recursive PROMPT_SUBST expansion.

Mitigation and Prevention

Immediate Steps to Take

Update zsh to version 5.8.1 or above
Avoid executing commands in a shell prompt from untrusted sources

Long-Term Security Practices

Regularly update software and apply patches promptly
Monitor and restrict command execution within prompts to trusted sources

Patching and Updates

Apply the latest patches and updates provided by zsh to address this vulnerability.