CVE-2021-44730: 
Linux Debian vulnerability analysis and mitigation

CVE-2021-44730 affects snapd version 2.54.2, a component used in Ubuntu and other Linux distributions. The vulnerability was discovered by the Qualys Research Team and disclosed on February 17, 2022. The issue stems from improper validation of the snap-confine binary location, which could allow a local attacker to execute arbitrary binaries and gain privilege escalation. This vulnerability was fixed in snapd versions 2.54.3+18.04, 2.54.3+20.04, and 2.54.3+21.10.1 (Ubuntu Notice, Debian Notice).

The vulnerability exists in snap-confine's scopensnapd_tool() function. The issue arises when snap-confine dynamically obtains the path to snap-update-ns and snap-discard-ns (helper programs executed with root privileges) by reading its own path via /proc/self/exe. The CVSS 3.1 base score is 7.8 (High) with the vector string CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H, indicating local access required, high attack complexity, low privileges required, and high impact on confidentiality, integrity, and availability (Openwall List).

If exploited, this vulnerability allows a local attacker to execute arbitrary binaries with elevated privileges, potentially leading to complete system compromise. The attack requires specific conditions, notably when the kernel's fs.protected_hardlinks is set to 0, which is not the default configuration in most distributions (Openwall List).

The vulnerability has been patched in snapd version 2.54.3. Users should upgrade to snapd versions 2.54.3+18.04, 2.54.3+20.04, or 2.54.3+21.10.1 depending on their Ubuntu version. For Debian users, fixes are available in version 2.37.4-1+deb10u1 for Debian 10 (buster) and version 2.49-1+deb11u1 for Debian 11 (bullseye). Fedora users should upgrade to snapd-2.54.3-1 (Fedora Update).