CVE-2020-26521: 
NixOS vulnerability analysis and mitigation

The JWT library in NATS nats-server before version 2.1.9 contains a vulnerability identified as CVE-2020-26521. This security issue was discovered and disclosed on November 2, 2020, affecting the JWT handling functionality in the NATS server. The vulnerability allows a denial of service condition through a nil dereference in Go code (Openwall Mailing, NVD).

The vulnerability is characterized by a nil pointer dereference in the JWT library implementation, which can trigger a Go panic condition. 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, indicating network accessibility with low attack complexity and no required privileges or user interaction (NVD).

When exploited, this vulnerability can result in a denial of service condition affecting the NATS server. The impact is primarily focused on service availability, with no direct impact on confidentiality or integrity of the system (NVD).

The vulnerability can be triggered remotely without requiring authentication or special privileges. The attack complexity is considered low, making it relatively straightforward to exploit (NVD).

The vulnerability has been fixed in NATS server version 2.1.9. Users are strongly advised to upgrade to this version or later to address the security issue. The fix was released on November 2, 2020, and has been incorporated into distribution packages such as Fedora (Fedora Update).