CVE-2023-29570

Vulnerability

A segmentation fault (SEGV) vulnerability exists in Cesanta MJS version 2.20.0 in the function mjs_ffi_cb_free at src/mjs_ffi.c:982:24. The bug is triggered when processing a specially crafted JavaScript file (poc5.js) provided as a proof-of-concept [1][2]. The crash occurs due to a read access to an invalid memory address.

Exploitation

An attacker can exploit this vulnerability by supplying a malicious JavaScript file to the mjs interpreter. No authentication or special privileges are required; the attacker only needs the ability to execute mjs with the crafted file as input. The provided PoC file poc5.js triggers the crash upon execution, as demonstrated by AddressSanitizer output [1][2].

Impact

Successful exploitation leads to a denial-of-service (DoS) condition through a segmentation fault, causing the mjs interpreter to crash. This can disrupt services or applications relying on the MJS library.

Mitigation

As of the available references, no official patch or fixed version has been released [1][2]. Users should monitor the Cesanta MJS repository for updates. If the application is exposed to untrusted input, consider restricting access or using alternative JavaScript engines until a fix is available.