CVE-2024-4771: 
NixOS vulnerability analysis and mitigation

A memory allocation check vulnerability (CVE-2024-4771) was discovered in Firefox versions prior to 126. The vulnerability was reported by Irvan Kurniawan and disclosed on May 14, 2024. This security flaw affects the Firefox web browser's memory handling system (Mozilla Advisory, NVD).

The vulnerability stems from a missing memory allocation check which could lead to a use-after-free condition if the allocation failed. The issue specifically involves the hb_blob_create_or_fail function where, when the hb_object_create calloc returns nullptr and the user_data is freed, the user_data could be reused by ForgetHashEntry code. The vulnerability has been assigned a CVSS v3.1 base score of 8.6 (High) with vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H (NVD).

If exploited, this vulnerability could trigger a crash or potentially be leveraged to achieve code execution. However, the real-world risk is considered relatively low as the allocation involved is only 48 bytes, and exploitation would require the system to be on the edge of memory exhaustion (Mozilla Bug).

The vulnerability is classified as moderately difficult to exploit. While it could potentially lead to code execution, the exploitation conditions are specific and challenging to achieve. The issue requires reaching a particular small-allocation failure without triggering an out-of-memory crash in the process (Mozilla Advisory).

The vulnerability has been fixed in Firefox version 126. The fix involves ensuring that the mSharedBlobData pointer is cleared in the failure case. Users are advised to upgrade to Firefox 126 or later versions to protect against this vulnerability (Mozilla Advisory).