CVE-2016-20013: 
Linux Ubuntu vulnerability analysis and mitigation

CVE-2016-20013 affects sha256crypt and sha512crypt implementations through version 0.6. The vulnerability was disclosed on February 19, 2022. This security issue impacts password hashing algorithms used in various systems and software packages, including glibc, dietlibc, sssd, and other systems that implement these cryptographic functions (NVD).

The vulnerability stems from a design flaw where the algorithm's runtime is proportional to the square of the password length, making it susceptible to denial of service attacks. The issue has been assigned a CVSS v3.1 base score of 7.5 (HIGH), with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. The vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling) (NVD, Ubuntu).

The primary impact of this vulnerability is the potential for denial of service attacks through CPU consumption. An attacker can exploit this vulnerability by submitting passwords of specific lengths, causing the system to spend disproportionate amounts of computational resources on the hashing operation. This can lead to system performance degradation or complete service unavailability (NVD).

As of current reports, there is no fixed version available for many affected systems. For Ubuntu systems, the vulnerability remains in a 'fix deferred' state. The recommended approach is to transition to more modern password hashing algorithms such as Argon2 or scrypt, which are designed to be more resistant to such attacks (Ubuntu).