PatchTheCVECVE-2026-33603: Attacker can use a specially crafted base64 exchange between Dovecot and Client to fake SCRAM TLS channel bind
CVE-2026-33603 is a medium-severity flaw (CVSS 6.8) affecting dovecot, dovecot. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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.
Why this priority
- No elevated risk signals yet
A fixed release or distro patch exists.
Risk facts
| CVSS score | 6.8 (Medium) |
| Attack vector | Adjacent network |
| Attack complexity | High |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.2% (top 88%) |
| CISA exploited list | No |
| Weakness | CWE-99 |
| Published | 2026-05-12 |
| Last modified | 2026-10-26 |
Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-33603?
dovecot: upgrade to 2.4.4; dovecot: upgrade to 3.1.5. Exact commands for each OS are on this page.
Is CVE-2026-33603 being exploited?
CVE-2026-33603 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-33603 affect?
CVE-2026-33603 affects dovecot, dovecot. Severity is medium (CVSS 6.8). 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 atta
How urgent is CVE-2026-33603?
Priority 27/100. No elevated risk signals yet.
Software pages
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