Heap-based Buffer Overflow in Apache HTTP Server (mod_xml2enc) - CVE-2026-42536
Summary
ALPINE-CVE-2026-42536: Heap-based Buffer Overflow vulnerability in Apache HTTP Server with mod_xml2enc, xml2StartParse, and untrusted content This issue affects Apache HTTP Server: from 2.4.0 through 2.4.67. Affects apache2 versions < 2.4.68-r0. Fixed in 2.4.68-r0. How to fix ↓
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Background
Apache HTTP Server is a widely-used open-source web server software that enables the hosting of websites and web applications. It is known for its flexibility, power, and extensive feature set, including support for various modules that enhance its functionality. The vulnerability in question affects versions 2.4.0 through 2.4.67 of the Apache HTTP Server, specifically related to the mod_xml2enc module, which handles XML encoding and decoding. This vulnerability can lead to severe security risks if exploited.
Vulnerability Detail
The vulnerability identified as CVE-2026-42536 is a heap-based buffer overflow that occurs in the Apache HTTP Server when processing untrusted content with the mod_xml2enc module. This flaw can be exploited by attackers to execute arbitrary code, potentially leading to a complete system compromise. The issue arises from improper handling of XML parsing, which can allow attackers to manipulate memory allocation and execution flow, resulting in significant security breaches.
How To Fix
Minimum fixed version
2.4.68-r0
This is the first release that contains the fix.
sudo apk add --upgrade apache2Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, users can disable the mod_xml2enc module if it is not essential for their application. This can be done by commenting out the relevant LoadModule directive in the Apache configuration file, typically located at /etc/httpd/conf/httpd.conf. For example, you can add a '#' before the line: '#LoadModule xml2enc_module modules/mod_xml2enc.so'.
Conclusion
CVE-2026-42536 represents a significant security risk for users of the Apache HTTP Server versions 2.4.0 through 2.4.67. It is crucial to upgrade to version 2.4.68 or later to mitigate this vulnerability. Users should also consider using tools like Vulert to monitor for vulnerabilities in their applications.
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FAQ
CVE-2026-42536 is a vulnerability in the Apache HTTP Server that allows for a heap-based buffer overflow, potentially leading to arbitrary code execution.
The vulnerability affects Apache HTTP Server versions from 2.4.0 to 2.4.67.
You can use Vulert to monitor and alert for open-source vulnerabilities in your software. Visit Vulert Scanner to check if your application is affected without any signup.
The CVSS score for CVE-2026-42536 is 7.5, indicating a high severity level.
If an immediate upgrade is not possible, consider disabling the mod_xml2enc module as a temporary workaround until you can apply the patch.
References
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