Vulnerability in Dovecot
CVE-2026-33603
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.8 (Medium). Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.
EPSS exploit prediction
EPSS: 0.002 (13.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 13th percentile — 13.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000
Affected products
Weakness classification (CWE)
References
- documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2… (vendor-advisory, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-33603?
- CVE-2026-33603 is a medium-severity vulnerability in Dovecot, classified under Resource Injection. CVSS score: 6.8/10. Published 2026-05-12.
- How severe is CVE-2026-33603?
- Medium severity. CVSS v3 base score is 6.8 out of 10.