CosmicSting: Magento Arbitrary File Read (CVE-2024-34102) + PHP Buffer Overflow in the iconv() function of glibc (CVE-2024-2961)

Description

This combination of an Arbitrary File Read (CVE-2024-34102) and a Buffer Overflow in glibc (CVE-2024-2961) allows for unauthenticated Remote Code Execution on the following versions of Magento and Adobe Commerce and earlier if the PHP and glibc versions are also vulnerable: - 2.4.7 and earlier - 2.4.6-p5 and earlier - 2.4.5-p7 and earlier - 2.4.4-p8 and earlier

Vulnerable PHP versions: - From PHP 7.0.0 (2015) to 8.3.7 (2024)

Vulnerable iconv() function in the GNU C Library: - 2.39 and earlier

The exploit chain is quite interesting and for more detailed information check out the references. The tl;dr being: CVE-2024-34102 is an XML External Entity vulnerability leveraging PHP filters to read arbitrary files from the target system. The exploit chain uses this to read /proc/self/maps, providing the address of PHP's heap and the libc's filename. The libc is then downloaded, and the offsets of libc_malloc, libc_system and libc_realloc are extracted, and made use of later in the chain.

With this information and expert knowledge of PHP's heap (chunks, free lists, buckets, bucket brigades), CVE-2024-2961 can be exploited. A long chain of PHP filters is constructed and sent in the same way the XXE is exploited, building a payload in memory and using the buffer overflow to execute it, resulting in an unauthenticated RCE.