CVE-2026-40019
Description
A flaw was found in Dovecot's ManageSieve login process. An unauthenticated attacker can exploit this vulnerability by sending a specially crafted, truncated quoted argument. This action causes the process to enter an infinite loop, consuming excessive CPU resources. Repeated exploitation can lead to a denial of service, impacting Sieve script management and overall server availability.
Mitigation
Restrict network access to the ManageSieve service to trusted clients only. This can be accomplished by configuring a firewall to limit incoming connections to the port used by ManageSieve (typically 4190/tcp) from known, authorized IP addresses or subnets. This action reduces the attack surface by preventing untrusted remote access to the vulnerable service. A service restart or reload may be required for firewall changes to take full effect, depending on the firewall management tool used.
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 | 7.5 | N/A | 5.9 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | High |
| 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:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Amplification
An infinite loop will cause unexpected consumption of resources, such as CPU cycles or memory. The software's operation may slow down, or cause a long time to respond.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
