Critical Dovecot Vulnerability: Denial of Service via Excessive IMAP Bracing
Summary
ALSA-2026:46532: Important: dovecot security update. Affects dovecot versions < 1:2.3.16-8.el8_10. Fixed in 1:2.3.16-8.el8_10. How to fix ↓
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Background
Dovecot is a widely used IMAP server designed for Linux and other UNIX-like systems, emphasizing security and performance. It also includes a POP3 server and supports email formats such as maildir and mbox. Dovecot is extensible with SQL drivers and authentication plugins, making it a versatile choice for email services. However, it is crucial to maintain its security to prevent potential exploits.
Vulnerability Detail
The vulnerability identified as CVE-2026-42006 allows for a Denial of Service (DoS) attack through excessive IMAP bracing. This issue arises when an attacker sends specially crafted IMAP commands that exploit the server's handling of braces, leading to resource exhaustion and service unavailability. The implications of this vulnerability can be severe, as it may disrupt email services for users and compromise the reliability of the Dovecot server.
How To Fix
Minimum fixed version
1:2.3.16-8.el8_10
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 limit the number of simultaneous connections to the Dovecot server or implement rate limiting on IMAP commands to mitigate the risk of exploitation until the patch is applied.
Conclusion
The Dovecot vulnerability CVE-2026-42006 poses a significant risk of Denial of Service attacks through excessive IMAP bracing. It is crucial to update to the patched version to safeguard your email services. Temporary workarounds can help mitigate risks until the update is applied.
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.
CVE-2026-42006 refers to a vulnerability in Dovecot that allows for Denial of Service attacks through excessive IMAP bracing.
You can check your Dovecot installation for vulnerabilities using tools like Vulert, which monitors open-source vulnerabilities in real-time.
Failure to address this vulnerability may lead to service outages, affecting email delivery and user access to email services.
Yes, implementing connection limits or rate limiting on IMAP commands can help mitigate the risk until the patch is applied.
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