Resource Exhaustion Vulnerability in Dovecot: CVE-2024-23185
Summary
ALPINE-CVE-2024-23185: Very large headers can cause resource exhaustion when parsing message. Affects dovecot versions < 2.3.21.1-r0. Fixed in 2.3.21.1-r0. How to fix ↓
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Background
Dovecot is an open-source IMAP and POP3 email server for Unix-like operating systems. It is designed to provide secure and efficient email retrieval and storage. Dovecot is known for its high performance, extensibility, and support for various authentication mechanisms. However, it is susceptible to a vulnerability that allows for resource exhaustion due to the handling of very large headers in email messages.
Vulnerability Detail
The vulnerability identified as CVE-2024-23185 arises from the message-parser's handling of large headers. When parsing messages, the message-header-parser builds a 'full_value' buffer from smaller chunks of the message. This buffer has no size limit, leading to potential excessive memory usage when processing large headers. Although incoming emails typically have size limits set by the Mail Transfer Agent (MTA), users can still append larger emails, which may lead to denial of service (DoS) for themselves and could cause memory issues for the backend. No known public exploits are available for this vulnerability.
How To Fix
Minimum fixed version
2.3.21.1-r0
This is the first release that contains the fix.
sudo apk add --upgrade dovecotTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a workaround, implement restrictions on header sizes at the MTA component preceding Dovecot. This can help mitigate the risk of resource exhaustion by limiting the size of headers that Dovecot has to process.
Conclusion
CVE-2024-23185 presents a significant resource exhaustion risk for Dovecot users, particularly when handling large email headers. It is crucial to update to the patched version to mitigate this vulnerability and consider implementing header size restrictions at the MTA level. Regular monitoring for vulnerabilities using tools like Vulert can help maintain the security of your applications.
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FAQ
CVE-2024-23185 is a vulnerability in Dovecot that allows for resource exhaustion due to the handling of very large email headers.
Users can experience denial of service (DoS) if they append large emails, leading to excessive memory usage and potential service disruption.
Yes, a patch is available in version 2.3.21.1-r0 of Dovecot. Users should update to this version or later.
Run the command 'apk add dovecot=2.3.21.1-r0' in your terminal to update to the patched version.
You can use Vulert, which monitors and alerts for open-source vulnerabilities in your software using just a manifest file. Check your application for vulnerabilities at Vulert Scanner.
References
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