CVE-2024-23775

Vulnerability

An integer overflow vulnerability exists in Mbed TLS versions 2.x before 2.28.7 and 3.x before 3.5.2. When parsing or writing x509 extensions, the function mbedtls_x509_set_extension() fails to validate the length input, which can lead to an integer overflow. This results in the allocation of a zero-length buffer on the heap, and subsequent copy of extension data into that buffer causes a heap buffer overflow [3].

Exploitation

An attacker can trigger the vulnerability by providing a crafted x509 extension with a specific length that causes the integer overflow. No special privileges are required beyond the ability to supply input to the extension parsing logic. The function mbedtls_x509_set_extension() is reachable when processing X.509 certificates or CSRs. A concrete sequence involves passing a length value that causes the internal arithmetic to wrap, resulting in a small or zero buffer allocation, followed by copying data that exceeds that allocation [3].

Impact

Successful exploitation leads to a heap buffer overflow, which typically results in a segmentation fault (segfault), causing a denial of service (DoS) of the application using Mbed TLS [1][3]. The impact is limited to availability (DoS) and does not provide code execution or information disclosure according to the available references.

Mitigation

Users should upgrade to Mbed TLS 2.28.7 (2.x branch) or 3.5.2 (3.x branch) as these versions contain the fix [3]. A workaround is to ensure that a length of SIZE_MAX cannot be passed into mbedtls_x509_set_extension(), though upgrading is strongly recommended [3]. No CISA KEV listing was identified for this CVE at the time of writing.