CVE-2026-33605
Description
A flaw was found in Dovecot. An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. This can lead to a denial of service for Sieve script management, affecting either the attacker's connection or all connections handled by the same process, depending on the security mode.
Mitigation
Restrict network access to the ManageSieve service to trusted clients only. This can be achieved by configuring a firewall to limit incoming connections to the service's port (e.g., 4190 for Sieve) from specific IP addresses or networks. For example, using `firewalld`:
bash
firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<TRUSTED_IP_OR_NETWORK>" port port="4190" protocol="tcp" accept'
firewall-cmd --reload
Replace `<TRUSTED_IP_OR_NETWORK>` with the actual trusted source. A firewall reload is required for changes to take effect.
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).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 7.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Other
Technical Impact: Varies by Context
Frequently Asked Questions
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