CVE-2021-33582: 
NixOS vulnerability analysis and mitigation

CVE-2021-33582 affects Cyrus IMAP before version 3.4.2, where a vulnerability in the string hashing algorithm used in internal hash tables allows remote attackers to cause a denial of service condition. The vulnerability was discovered in 2021 and fixed in versions 3.4.2, 3.2.8, and 3.0.16 (NVD, RedHat).

The vulnerability stems from a flawed string hashing algorithm used in internal hash tables that allows user inputs to be stored in predictable buckets. When many insertions occur into a single bucket, the strcmp operation becomes slow, leading to performance degradation. The issue has a CVSS v3.1 base score of 7.5 (High), with attack vector being Network, attack complexity Low, and requiring no privileges or user interaction (Ubuntu).

When exploited, this vulnerability can cause the Cyrus IMAP daemon to hang for multiple minutes, effectively creating a denial of service condition that impacts service availability. The impact is limited to availability, with no effect on confidentiality or integrity of the system (NVD).

The vulnerability has been fixed in Cyrus IMAP versions 3.4.2, 3.2.8, and 3.0.16. Users are advised to upgrade to these or later versions. Various Linux distributions have also released security updates to address this vulnerability, including Red Hat Enterprise Linux 8 and Fedora (RedHat, Fedora).