CVE-2020-13619

Overview

CVE-2020-13619 is a command injection vulnerability in the php/exec/escapeshellarg function of the Locutus library (versions up to 2.0.11). Locutus provides TypeScript implementations of PHP standard library functions, including shell argument escaping. The root cause is insufficient sanitization of single quotes, allowing an attacker to break out of the intended argument boundary and inject arbitrary shell commands.

Exploitation

The vulnerability is exploited by passing a crafted string containing two consecutive single characters ('') to the escapeshellarg function. Due to the flawed escaping logic, these characters are not properly handled, enabling an attacker to close the escaping context and append malicious shell commands. No authentication is required if the vulnerable function is exposed to user input; the attacker simply needs to supply the crafted input to an application that uses Locutus escapeshellarg to sanitize shell arguments [1][2].

Impact

Successful exploitation allows an attacker to achieve arbitrary code execution on the server or client environment where the vulnerable function is invoked. This can lead to full system compromise, data exfiltration, or further lateral movement, depending on the privileges of the running process [2][3].

Mitigation

The vendor was contacted on May 27, 2020, but after 30 days with no response, the issue was publicly disclosed on July 1, 2020 [3]. A proof-of-concept is available. Users should verify if their application uses the affected function and either patch to a fixed version (if available from the vendor) or implement additional input validation. This vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog at the time of this writing.