CVE-2026-27857 Details
Description
Sending "NOOP (((...)))" command with 4000 parenthesis open+close results in ~1MB extra memory usage. Longer commands will result in client disconnection. This 1 MB can be left allocated for longer time periods by not sending the command ending LF. So attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Attacker could connect possibly from even a single IP and create 1000 connections to allocate 1 GB of memory, which would likely result in reaching VSZ limit and killing the process and its other proxied connections. Install fixed version, there is no other remediation. No publicly available exploits are known.
A denial-of-service vulnerability has been identified in Open-Xchange Dovecot Pro and Community Edition versions 2.3.0, 3.0.2, 3.1.0, and 2.4.0. The issue arises when the NOOP command is sent with approximately 4000 parentheses, leading to an excessive memory allocation of around 1MB per connection. This additional memory usage can persist if the command is not terminated with a line feed, allowing an attacker to create multiple connections and potentially exhaust the server's memory resources. Such exploitation could disrupt the Dovecot process and its proxied connections, causing a denial-of-service condition.
Users are advised to upgrade to a fixed version. For OX Dovecot Pro, the fixed version is 3.0.5, 3.1.4, and 2.3.22.1. For OX Dovecot CE, the fixed version is 2.4.3.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Mar 27, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-400 | Uncontrolled Resource Consumption | [email protected] |
| CWE-770 | Allocation of Resources Without Limits or Throttling | redhat-SADP |
Affected Products
| Product | Versions |
|---|---|
| dovecot dovecot | < 2.4.3 |
CPE
Remediation
| |
| open-xchange dovecot | < 2.3.22.1 >= 3.0.0, < 3.0.5 >= 3.1.0, < 3.1.4 |
CPE
Remediation
| |
Change History
6 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 15, 2026 | CVE Modified | redhat-SADP |
| Jun 30, 2026 | CVE Modified | redhat-SADP |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Apr 30, 2026 | Initial Analysis | [email protected] |
| Mar 27, 2026 | New CVE Received | [email protected] |