CVE-2026-33603
Description
A flaw was found in Dovecot. An attacker, positioned as a Man-in-the-Middle (MITM) between Dovecot and a client, can exploit a specially crafted base64 exchange to fake SCRAM TLS channel binding. This allows the attacker to eavesdrop on communications between Dovecot and the client, leading to information disclosure.
Mitigation
To reduce the risk of a Man-in-the-Middle attack, restrict network access to the Dovecot server. Configure firewalls to permit connections only from trusted networks and necessary client IP ranges. This limits an attacker's ability to intercept traffic. If firewall rules are modified, a service reload or restart may be required, which could temporarily disrupt active user sessions.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.8 | 5.3 | 6.8 |
| Attack Vector | Adjacent Network | Adjacent Network | Adjacent Network |
| Attack Complexity | High | High | High |
| Privileges Required | None | None | None |
| User Interaction | None | None | None |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | High | High | High |
| Integrity Impact | High | None | High |
| Availability Impact | None | None | None |
Vector
Red Hat: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
NVD: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
cve.org: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Understanding the Weakness (CWE)
Access Control,Other
Technical Impact: Gain Privileges or Assume Identity; Varies by Context; Bypass Protection Mechanism
An attacker can access any functionality that is inadvertently accessible to the source.
Frequently Asked Questions
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