HOMEVULNERABILITIESCVE-2021-33582
HIGH

CVE-2021-33582

CWE-407Published: September 1, 2021· Updated: Jun 17, 2026

7.5
CVSS v3.1

Official 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.

NVD Source

Technical Analysis

CVE-2021-33582 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in availability disruption (denial of service), with a CVSS base score of 7.5.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.None
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityHigh
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected Vendors & Products

cyrus1 product(s)
imap
Debian1 product(s)
debian linux
Fedora1 product(s)
fedora
Source: NVD CPE · 4 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://cyrus.topicbox.com/groups/announce/T3dde0a2352462975-M1386fc44adf967e072f8df13/cyrus-imap-3-4-2-3-2-8-and-3-0-16-released
PATCHhttps://github.com/cyrusimap/cyrus-imapd/commits/master
PATCHhttps://www.cyrusimap.org/imap/download/release-notes/index.html
PATCHhttps://cyrus.topicbox.com/groups/announce/T3dde0a2352462975-M1386fc44adf967e072f8df13/cyrus-imap-3-4-2-3-2-8-and-3-0-16-released
PATCHhttps://github.com/cyrusimap/cyrus-imapd/commits/master
PATCHhttps://www.cyrusimap.org/imap/download/release-notes/index.html
ADVISORYhttps://github.com/cyrusimap/cyrus-imapd/security/advisories
ADVISORYhttps://lists.debian.org/debian-lts-announce/2022/06/msg00013.html
ADVISORYhttps://github.com/cyrusimap/cyrus-imapd/security/advisories
ADVISORYhttps://lists.debian.org/debian-lts-announce/2022/06/msg00013.html

All References (14)

→
https://cyrus.topicbox.com/groups/announce/T3dde0a2352462975-M1386fc44adf967e072f8df13/cyrus-imap-3-4-2-3-2-8-and-3-0-16-releasedPatch · Vendor Advisory
→
https://github.com/cyrusimap/cyrus-imapd/commits/masterPatch · Third Party Advisory
→
https://github.com/cyrusimap/cyrus-imapd/security/advisoriesNot Applicable · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2022/06/msg00013.htmlMailing List · Third Party Advisory
→
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.htmlPatch · Release Notes · Vendor Advisory
→
https://cyrus.topicbox.com/groups/announce/T3dde0a2352462975-M1386fc44adf967e072f8df13/cyrus-imap-3-4-2-3-2-8-and-3-0-16-releasedPatch · Vendor Advisory
→
https://github.com/cyrusimap/cyrus-imapd/commits/masterPatch · Third Party Advisory
→
https://github.com/cyrusimap/cyrus-imapd/security/advisoriesNot Applicable · Third Party Advisory
→
https://lists.debian.org/debian-lts-announce/2022/06/msg00013.htmlMailing List · Third Party Advisory
→
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.htmlPatch · Release Notes · Vendor Advisory

Quick Facts

CVE IDCVE-2021-33582
CVSS Score7.5 / 10
SeverityHIGH
WeaknessCWE-407
CISA KEVNo
Affected3 vendor(s)
PublishedSep 1, 2021

Related CVEs (CWE-407)

CVE-2026-57480
8.7
CVE-2026-58226
8.7
CVE-2026-54892
8.7
CVE-2026-55206
8.7
CVE-2026-43967
8.7
CVE-2020-3548
7.5

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-33582 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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