Critical Denial of Service Vulnerability in Dovecot IMAP Server
Summary
ALSA-2026:41988: Important: dovecot security update. Affects dovecot versions < 1:2.3.21-19.el10_2.1. Fixed in 1:2.3.21-19.el10_2.1. How to fix ↓
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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 email storage in maildir or mbox formats. Dovecot is modular, allowing for various SQL drivers and authentication plugins, making it a flexible choice for email management. However, it is susceptible to vulnerabilities that can compromise its stability and security.
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 requests that exploit the server's handling of IMAP commands, potentially leading to service interruptions and degraded performance. The implications of this vulnerability are significant, as it can render the email service unavailable to legitimate users, impacting communication and operations.
How To Fix
Minimum fixed version
1:2.3.21-19.el10_2.1
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 measure, administrators can limit the number of simultaneous connections to the Dovecot server or implement rate limiting on IMAP requests to reduce the risk of exploitation until the package is updated.
Conclusion
The Dovecot security update addresses a critical Denial of Service vulnerability that can severely impact email services. It is crucial for users to update their installations to the patched version to ensure continued security and performance. Utilizing tools like Vulert can further enhance vulnerability management in open-source applications.
See every vulnerability recorded for dovecot →
FAQ
CVE-2026-42006 is a vulnerability in Dovecot that allows for Denial of Service attacks via excessive IMAP bracing.
You can check your Dovecot version and compare it against the patched version '1:2.3.21-19.el10_2.1'. Alternatively, use the Vulert playground to monitor for vulnerabilities.
Failure to address this vulnerability can lead to service outages, affecting email communication and potentially exposing sensitive data.
Yes, you can use Vulert, which monitors open-source vulnerabilities in real-time using a manifest file like package-lock.json.
If immediate updates are not possible, consider implementing rate limiting on IMAP requests and limiting simultaneous connections to mitigate the risk.
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