CVE-2021-3697: 
NixOS vulnerability analysis and mitigation

A vulnerability was discovered in GRUB2 (CVE-2021-3697) affecting versions prior to GRUB-2.12. The flaw involves the JPEG image handling functionality where a crafted JPEG image may lead the JPEG reader to underflow its data pointer, allowing user-controlled data to be written in the heap (Debian Security, Ubuntu Security).

The vulnerability occurs when handling JPEG images in GRUB2, where a specially crafted image can cause a buffer underwrite allowing arbitrary data to be written to the heap. For successful exploitation, an attacker needs to perform triage over the heap layout and craft an image with a malicious format and payload. The vulnerability has been assigned a CVSS score of 7.0 (HIGH) with the vector CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H (NetApp Security).

The successful exploitation of this vulnerability can lead to data corruption and potential code execution or secure boot circumvention. The impact includes the possibility of disclosure of sensitive information, addition or modification of data, or Denial of Service (DoS) (Debian Security, NetApp Security).

The vulnerability has been fixed in GRUB2 version 2.12 and later. Users are advised to upgrade to the latest version of GRUB2. For Ubuntu systems, specific package versions have been released to address this vulnerability, including updates for Ubuntu 22.04 and 20.04 LTS (Ubuntu Security).