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CVE-2026-33603

22
FAUCET Score

Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel binding. This requires that the attacker is able to position itself between Dovecot and the client connection. If successful, the attacker can eavesdrop communications between Dovecot and client as MITM proxy. Install fixed version. No publicly available exploits are known.

First published: May 12, 2026Last modified: May 12, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 2.4.4CPE matchmatch criteria
cpe:2.3:a:dovecot:dovecot:*:*:*:*:*:*:*:*
< 3.1.5CPE matchmatch criteria
cpe:2.3:a:open-xchange:dovecot:*:*:*:*:pro:*:*:*

CVSS Data

CVSS version used by this source: 3.1

6.8MEDIUM

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

Attack Vector
ADJACENT_NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
1.6
Impact Score
5.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.22%
Probability of exploitation in next 30 days
EPSS Percentile
12.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0022 is in the 5th percentile among its peer group of 1,749 CVEs.

Social Chatter

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

Media Mentions

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)

ubuntupatch availablevia ubuntu_usn
Product: dovecot (jammy)Fixed in: 1:2.3.16+dfsg1-3ubuntu2.9
ubuntupatch availablevia ubuntu_usn
Product: dovecot (noble)Fixed in: 1:2.3.21+dfsg1-2ubuntu6.5
ubuntupatch availablevia ubuntu_usn
Product: dovecot (questing)Fixed in: 1:2.4.1+dfsg1-5ubuntu4.2
ubuntupatch availablevia ubuntu_usn
Product: dovecot (resolute)Fixed in: 1:2.4.2+dfsg1-3ubuntu2.1

Vendor Advisories (1)

ubuntuUSN-8365-1

Dovecot vulnerabilities

Jun 2, 2026

References

documentation.open-xchange.com / dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0002.json
Vendor Advisory