CVE-2026-42006
Description
A flaw was found in Dovecot. A remote attacker can exploit this vulnerability by sending excessive open braces over the Internet Message Access Protocol (IMAP), leading to uncontrolled memory usage. This can cause the affected system to consume memory up to its configured limit, resulting in a Denial of Service (DoS).
Statement
A remote attacker can trigger this flaw simply by sending specially crafted IMAP requests to the Dovecot server, requiring no complex interactions.
The vulnerability is strictly limited to a Denial of Service (DoS) via memory exhaustion and does not allow for data exfiltration, privilege escalation, or remote code execution. Furthermore, the impact is contained because the memory consumption is restricted to the process's configured limit, preventing a complete system-wide crash.
Mitigation
To mitigate this issue, administrators can configure the `vsz_limit` setting for the Dovecot IMAP process to a lower value. This limits the virtual memory size available to the IMAP process, preventing excessive memory consumption.
Example configuration in `/etc/dovecot/conf.d/10-master.conf`:
service imap {
vsz_limit = 256M
}
After modifying the configuration, restart the Dovecot service for the changes to take effect.bashSetting `vsz_limit` too low may impact legitimate IMAP operations.
systemctl restart dovecot
*Restarting the dovecot service will temporarily interrupt mail services.
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)
Availability
Technical Impact: DoS: Resource Consumption (CPU); DoS: Resource Consumption (Memory); DoS: Resource Consumption (Other)
When allocating resources without limits, an attacker could prevent other systems, applications, or processes from accessing the same type of resource. It can be easy for an attacker to consume many resources by rapidly making many requests or causing larger resources to be used than is needed.
Frequently Asked Questions
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