What’s Vulnerable › Vulnerabilities

CVE-2021-33582

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 3.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-09-01 · updated 2026-06-17
• Weakness: CWE-407

Description

Cyrus IMAP before 3.4.2 allows remote attackers to cause a denial of service (multiple-minute daemon hang) via input that is mishandled during hash-table interaction. Because there are many insertions into a single bucket, strcmp becomes slow. This is fixed in 3.4.2, 3.2.8, and 3.0.16.

Affected products

• cyrusimap Cyrus IMAP: before 3.0.16; from 3.2.0 before 3.2.8; from 3.4.0 before 3.4.2 — fixed in 3.0.16, 3.2.8, 3.4.2
• Debian Linux: 9.0
• Fedoraproject Fedora: 34, 35

How to fix

Upgrade to a fixed version: cyrusimap Cyrus IMAP 3.0.16, 3.2.8, 3.4.2. Check the vendor advisory for mitigations.

References

• https://cyrus.topicbox.com/groups/announce/T3dde0a2352462975-M1386fc44adf967e072f8df13/cyrus-imap-3-4-2-3-2-8-and-3-0-16-released
• https://github.com/cyrusimap/cyrus-imapd/commits/master
• https://github.com/cyrusimap/cyrus-imapd/security/advisories
• https://lists.debian.org/debian-lts-announce/2022/06/msg00013.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6HEO3RURJW6NLIXS7NK5PVU6MGHC4SCM/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WJZB45QBUN7CZFGOWCZYUYACNBTX7LVS/
• https://www.cyrusimap.org/imap/download/release-notes/index.html
• https://cyrus.topicbox.com/groups/announce/T3dde0a2352462975-M1386fc44adf967e072f8df13/cyrus-imap-3-4-2-3-2-8-and-3-0-16-released
• https://github.com/cyrusimap/cyrus-imapd/commits/master
• https://github.com/cyrusimap/cyrus-imapd/security/advisories
• https://lists.debian.org/debian-lts-announce/2022/06/msg00013.html
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6HEO3RURJW6NLIXS7NK5PVU6MGHC4SCM/

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