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Fencer Vulns
high 7.5

CVE-2021-33582 json

Cyrus IMAP before 3.4.2 allows remote attackers to cause a denial of service (multiple-minute daemon hang) via input that is mishandled dur…

published 2021-09-01 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-20268

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.1%
EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits
0
none known

Summary

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.

Patch / fix

  • cyrus imap 3.0.16, 3.2.8, 3.4.2
  • cyrus-imapd Debian 14, Debian 13, Debian 12 3.4.2-1

debian advisories DEBIAN-CVE-2021-33582

  • cyrus-imapd Ubuntu Pro 18.04 LTS 2.5.10-3ubuntu1.1+esm1
  • cyrus-imapd Ubuntu Pro 20.04 LTS 3.0.13-5ubuntu0.1~esm1

ubuntu advisories UBUNTU-CVE-2021-33582

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • cyrus-imapd RHEL 8 3.0.7-20.el8_4.1
  • cyrus-imapd-vzic RHEL 8 3.0.7-20.el8_4.1
  • cyrus-imapd-utils RHEL 8 3.0.7-20.el8_4.1
  • cyrus-imapd RHEL 8.1 EUS 3.0.7-16.el8_1.1
  • cyrus-imapd-vzic RHEL 8.1 EUS 3.0.7-16.el8_1.1
  • cyrus-imapd-utils RHEL 8.1 EUS 3.0.7-16.el8_1.1
  • cyrus-imapd RHEL 8.2 EUS 3.0.7-16.el8_2.1
  • cyrus-imapd-vzic RHEL 8.2 EUS 3.0.7-16.el8_2.1

red hat advisories RHSA-2021:3546RHSA-2021:3492RHSA-2021:3493

  • cyrus-imapd openSUSE Tumbleweed 2.4.22-2.1

opensuse advisories openSUSE-SU-2024:11901-1

  • cyrus-imapd Rocky Linux 8 3.0.7-20.el8_4.1

rocky linux advisories RLSA-2021:3492

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-33582 updated cvss 7.5

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

  • Red Hat Enterprise Linux 6 cyrus-imapd, cyrus-imapd-utils Red Hat Enterprise Linux 7 cyrus-imapd, cyrus-imapd-utils
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AppStream (v. 8) cyrus-imapd 3.0.7-20.el8_4.1, cyrus-imapd-vzic 3.0.7-20.el8_4.1, cyrus-imapd-utils 3.0.7-20.el8_4.1
    fixed: vendor fix RHSA-2021:3492
  • Red Hat Enterprise Linux AppStream EUS (v. 8.1) cyrus-imapd 3.0.7-16.el8_1.1, cyrus-imapd-vzic 3.0.7-16.el8_1.1, cyrus-imapd-utils 3.0.7-16.el8_1.1
    fixed: vendor fix RHSA-2021:3546
  • Red Hat Enterprise Linux AppStream EUS (v. 8.2) cyrus-imapd 3.0.7-16.el8_2.1, cyrus-imapd-vzic 3.0.7-16.el8_2.1, cyrus-imapd-utils 3.0.7-16.el8_2.1
    fixed: vendor fix RHSA-2021:3493
  • Red Hat Enterprise Linux 9 perl-Cyrus, cyrus-imapd, cyrus-imapd-libs, cyrus-imapd-utils
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.09% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness
  • CWE-407 Inefficient Algorithmic Complexity

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.