Moderate Vulnerability in mod_md: Unrestricted OCSP Response Leading to Resource Exhaustion
Summary
ALSA-2026:30844: Moderate: mod_md security update. Affects mod_md versions < 1:2.4.26-2.el9_8.1. Fixed in 1:2.4.26-2.el9_8.1. How to fix ↓
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Background
mod_md is a module designed for managing common properties of domains across one or more virtual hosts. It utilizes the ACME protocol to automate the provisioning of SSL/TLS certificates, ensuring that certificates for managed domains and their virtual hosts are configured automatically, including during renewal processes. This functionality is crucial for maintaining secure communications over the internet.
Vulnerability Detail
The vulnerability identified as CVE-2026-29168 involves an unrestricted OCSP (Online Certificate Status Protocol) response, which can lead to resource exhaustion. This means that an attacker could exploit this weakness to overwhelm the server's resources, potentially causing service disruptions or outages. The issue arises from the way mod_md handles OCSP responses, allowing for excessive resource consumption under certain conditions.
How To Fix
Minimum fixed version
1:2.4.26-2.el9_8.1
This is the first release that contains the fix.
sudo dnf update mod_mdTip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
Currently, no specific workarounds are provided for this vulnerability. The best course of action is to apply the available patch as soon as possible.
Conclusion
In summary, the mod_md module has a moderate vulnerability (CVE-2026-29168) that can lead to resource exhaustion due to unrestricted OCSP responses. It is crucial to update to the patched version to mitigate this risk. Regular updates and monitoring for vulnerabilities are essential for maintaining system security.
See every vulnerability recorded for mod_md →
FAQ
mod_md is a module for Apache HTTP Server that automates the management of SSL/TLS certificates using the ACME protocol.
CVE-2026-29168 refers to a vulnerability in mod_md that allows for unrestricted OCSP responses, leading to potential resource exhaustion.
You can use the Vulert platform to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected without needing to sign up.
The potential impacts include service disruptions and outages due to resource exhaustion, which can affect the availability of your web services.
It is recommended to regularly check for updates and apply them promptly to ensure your system is protected against known vulnerabilities.
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