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CVE-2026-33603

MEDIUMCVSS 5.3/10EPSS 0.22%

Last modified

CVE-2026-33603 is a medium-severity vulnerability rated 5.3/10 on the CVSS scale. 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. EPSS estimates a 0.22% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
5.3/10

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

EPSS Probability
0.22%

12.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
DovecotDovecot< 2.4.4
Open-XchangeDovecot< 3.1.5

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is 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.
How severe is CVE-2026-33603?
CVE-2026-33603 has a CVSS score of 5.3/10 (MEDIUM severity). The EPSS model estimates a 0.22% probability of exploitation in the next 30 days.
How do I fix CVE-2026-33603?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-33603?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST