CVE-2020-11501: 
NixOS vulnerability analysis and mitigation

CVE-2020-11501 affects GnuTLS versions 3.6.x before 3.6.13, with the earliest affected version being 3.6.3 (2018-07-16). The vulnerability was introduced by an error in a 2017-10-06 commit that caused the DTLS client to always use 32 '\0' bytes instead of a random value during DTLS negotiation (GnuTLS Advisory).

The vulnerability stems from an implementation flaw where the DTLS client fails to contribute any randomness to the DTLS negotiation process. Specifically, instead of generating random values, the client always uses 32 null bytes ('\0') in the DTLS client hello message. This has been assigned a CVSS v3.1 base score of 7.4 (HIGH) with the vector AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N (NVD).

The vulnerability breaks the security guarantees of the DTLS protocol by compromising the randomness required for secure cryptographic operations. This could allow attackers to potentially predict or manipulate the cryptographic parameters, leading to the disclosure of sensitive information or modification of data (NetApp Advisory).

The vulnerability was fixed in GnuTLS version 3.6.13. Users and organizations are strongly recommended to upgrade to this version or later to address the security issue. Multiple vendors have released security updates including Debian, Ubuntu, Red Hat, and others to patch this vulnerability (Debian Advisory, Ubuntu Advisory).