Critical Use-After-Free Vulnerability in OpenSMTPD: Denial of Service and Remote Code Execution Risk
Summary
DEBIAN-CVE-2015-7687: Use-after-free vulnerability in OpenSMTPD before 5.7.2 allows remote attackers to cause a denial of service (crash) or execute arbitrary code via vectors involving req_ca_vrfy_smtp and req_ca_vrfy_mta. Affects opensmtpd versions < 5.7.3p1-1. Fixed in 5.7.3p1-1. How to fix ↓
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Background
OpenSMTPD is an open-source implementation of the Simple Mail Transfer Protocol (SMTP) that is designed to be secure, easy to configure, and efficient. It is widely used for sending and receiving emails. The package is known for its simplicity and adherence to security best practices. However, it has been found to have a critical vulnerability that could allow attackers to exploit the system, leading to potential denial of service or arbitrary code execution.
Vulnerability Detail
The vulnerability identified as CVE-2015-7687 is a use-after-free issue present in OpenSMTPD versions prior to 5.7.2. This flaw allows remote attackers to manipulate memory, potentially leading to a crash of the service or execution of arbitrary code. The vulnerability arises from improper handling of certain requests, specifically req_ca_vrfy_smtp and req_ca_vrfy_mta, which can be exploited to gain unauthorized access or disrupt service.
How To Fix
Minimum fixed version
5.7.3p1-1
This is the first release that contains the fix.
sudo apt-get install --only-upgrade opensmtpdTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
If immediate patching is not possible, consider disabling the affected features or restricting access to the OpenSMTPD service until the update can be applied. This may involve modifying firewall rules or service configurations to limit exposure.
Conclusion
The CVE-2015-7687 vulnerability in OpenSMTPD poses significant risks, including denial of service and potential remote code execution. It is crucial for users to update to the patched version to mitigate these risks. Regular monitoring and vulnerability management practices, such as using tools like Vulert, can help maintain the security of your applications.
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FAQ
CVE-2015-7687 is a use-after-free vulnerability in OpenSMTPD that can lead to denial of service or arbitrary code execution.
You can check your OpenSMTPD version by running 'opensmtpd -V' in the terminal. If it is below 5.7.3p1-1, it is vulnerable.
The risks include potential service crashes and the ability for attackers to execute arbitrary code on the server, compromising security.
Yes, you can use Vulert, which monitors and alerts for open-source vulnerabilities in real-time using a manifest file like package-lock.json.
Detailed information about CVE-2015-7687 can be found in the Debian CVE database and other security advisories.
References
Related vulnerabilities
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