CVE-2021-33582

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.

Published: 2021-09-01 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-33582 is rated Moderate Risk (56.3/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.02%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-33582

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-04 1.64% 1.02% -0.61%
2 2026-03-03 4.40% 1.64% -2.76%
3 2025-12-28 — 4.40% —

Full EPSS history (28 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-33582

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-33582

OS Trackers for CVE-2021-33582

vendor priority summary link
debian not yet assigned CVE-2021-33582 not yet assigned priority: Debian including 1 source packages (cyrus-imapd), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-33582
redhat high — https://access.redhat.com/security/cve/CVE-2021-33582
suse high CVE-2021-33582 severity important: SUSE including 14 source package names (cyradm-2.4.22-2.1, cyrus-imapd-2.3.11-60.65.71.6.1, …), 17 product×package rows across 4 product lines (SUSE Liberty Linux 8, SUSE Linux Enterprise Server 11 SP1-TERADATA, SUSE Linux Enterprise Server 11 SP3-TERADATA, openSUSE Tumbleweed): Fixed 17. https://www.suse.com/security/cve/CVE-2021-33582/
ubuntu medium CVE-2021-33582 medium priority: Ubuntu including 2 source packages (cyrus-imapd, cyrus-imapd-2.4), 22 status rows across 11 suites (bionic, focal, jammy, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): DNE 10, not-affected 6, released 4, ignored 1, needed 1. https://ubuntu.com/security/CVE-2021-33582

Affected software / configurations for CVE-2021-33582

Vendor Product Version Raw CPE
cyrus imap < 3.0.16 cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*
cyrus imap >= 3.2.0, < 3.2.8 cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*
cyrus imap >= 3.4.0, < 3.4.2 cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*
fedoraproject fedora 34 cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
fedoraproject fedora 35 cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

References for CVE-2021-33582

URL Tags
https://cyrus.topicbox.com/groups/announce/T3dde0a2352462975-M1386fc44adf967e072f8df13/cyrus-imap-3-4-2-3-2-8-and-3-0-16-released Patch Vendor Advisory
https://github.com/cyrusimap/cyrus-imapd/commits/master Patch Third Party Advisory
https://github.com/cyrusimap/cyrus-imapd/security/advisories Not Applicable Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/06/msg00013.html Mailing 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.html Patch Release Notes Vendor Advisory
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