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CVE-2021-33582

26
FAUCET Score

CVE-2021-33582 is a denial-of-service vulnerability affecting Cyrus IMAP versions prior to 3.4.2, 3.2.8, and 3.0.16, as well as various Debian and Fedora distributions. Attackers can remotely trigger a daemon hang lasting several minutes by sending specially crafted input that causes inefficient hash-table interactions. This vulnerability has a CVSS score of 7.5 (High), indicating a network-based attack with low complexity and high availability impact, but no confidentiality or integrity impact. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 3.0.16CPE matchmatch criteria
cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*
>= 3.2.0, < 3.2.8CPE matchmatch criteria
cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*
>= 3.4.0, < 3.4.2CPE matchmatch criteria
cpe:2.3:a:cyrus:imap:*:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
35CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

7.5HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.1

Exploit Intelligence

EPSS Score
3.07%
Probability of exploitation in next 30 days
EPSS Percentile
86.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0307 is in the 75th percentile among its peer group of 51,551 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

github_advisorypatch availablevia nvd_reference
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8Fixed in: cyrus-imapd-0:3.0.7-20.el8_4.1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.1 Extended Update SupportFixed in: cyrus-imapd-0:3.0.7-16.el8_1.1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 8.2 Extended Update SupportFixed in: cyrus-imapd-0:3.0.7-16.el8_2.1
View patch

Vendor Advisories (1)

redhatCVE-2021-33582Important

cyrus-imapd: Denial of service via string hashing algorithm collisions

Sep 1, 2021

References

cyrus.topicbox.com / groups/announce/T3dde0a2352462975-M1386fc44adf967e072f8df13/cyrus-imap-3-4-2-3-2-8-and-3-0-16-released
PatchVendor Advisory
github.com / cyrusimap/cyrus-imapd/commits/master
PatchThird Party Advisory
github.com / cyrusimap/cyrus-imapd/security/advisories
Not ApplicableThird Party Advisory
lists.debian.org / debian-lts-announce/2022/06/msg00013.html
Mailing ListThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/6HEO3RURJW6NLIXS7NK5PVU6MGHC4SCM
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/WJZB45QBUN7CZFGOWCZYUYACNBTX7LVS
cyrusimap.org / imap/download/release-notes/index.html
PatchRelease NotesVendor Advisory