Critical Security Update for Dovecot: Addressing Denial of Service Vulnerabilities
Summary
ALSA-2026:13857: Important: dovecot security update. Affects dovecot versions < 1:2.3.16-15.el9_7.1. Fixed in 1:2.3.16-15.el9_7.1. How to fix ↓
Check if this vulnerability affects your application
Upload a manifest or SBOM and we'll show whether you're affected, plus every other risky package in the same scan.
No signup required · Results in about 60 seconds
Background
Dovecot is a widely used IMAP server designed for Linux and UNIX-like systems, emphasizing security and performance. It also includes a POP3 server and supports various email formats, such as maildir and mbox. Dovecot is known for its extensibility through SQL drivers and authentication plugins, making it a popular choice for email services. However, recent vulnerabilities have been identified that could potentially compromise its stability and security.
Vulnerability Detail
The vulnerabilities in Dovecot stem from improper handling of specific commands and crafted messages, leading to Denial of Service (DoS) conditions. The issues include a crafted SASL initial response in the AUTHENTICATE command (CVE-2025-59032), crafted messages before authentication (CVE-2026-27858), and specially crafted NOOP commands (CVE-2026-27857). These vulnerabilities can cause the server to become unresponsive, affecting email services and user access.
How To Fix
Minimum fixed version
1:2.3.16-15.el9_7.1
This is the first release that contains the fix.
sudo dnf update dovecotTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, you may consider limiting access to the Dovecot server or implementing rate limiting on the AUTHENTICATE command to mitigate the impact of these vulnerabilities until the update can be applied.
Conclusion
In summary, the recent vulnerabilities in Dovecot pose significant risks to email services, leading to potential Denial of Service conditions. It is essential to update to the patched version to safeguard your systems. Additionally, utilizing tools like Vulert can help monitor and alert for open-source vulnerabilities effectively.
See every vulnerability recorded for dovecot →
FAQ
Dovecot is an open-source IMAP and POP3 server for Unix-like operating systems, designed with a focus on security and performance.
The vulnerabilities can lead to Denial of Service, making the email server unresponsive and disrupting email services for users.
You can use Vulert's playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
Yes, you can limit access to the Dovecot server or implement rate limiting on specific commands as a temporary measure.
It is recommended to regularly check for updates and apply them promptly to ensure your software is secure against known vulnerabilities.
Related vulnerabilities
Recent vulnerabilities recorded for dovecot.
