Overview
Apache HTTP Server has released critical security updates to address a race condition vulnerability in the mod_http2 module, which could be exploited to achieve remote code execution (RCE). This vulnerability, tracked as CVE-2026-119618, impacts Apache HTTP Server versions 2.4.55 through 2.4.70 and standalone mod_h2 versions 2.0.8 through 2.0.42. The Apache Software Foundation has released these patches to mitigate the risk of unauthorized code execution.
Vulnerability Details
The issue stems from a race condition in the mod_http2 module, specifically within the assign_headers() function. This race condition can lead to heap memory corruption, which can ultimately result in remote code execution (RCE) if exploited by an unauthenticated attacker. The vulnerability is particularly concerning because it can be triggered by concurrent threads sharing resources, allowing attackers to corrupt the heap memory and execute arbitrary commands with the privileges of the web server process.
Impact and Exposure
The Apache HTTP Server is a widely used open-source web server that handles requests from web browsers and serves website content. The vulnerability affects a significant number of servers, with a substantial portion of these servers being reachable over the public internet. According to telemetry data from cloud security company Wiz, 64% of cloud environments have vulnerable resources, and roughly half of them have publicly exposed instances. However, the numbers do not account for server configuration, which requires HTTP/2 to be enabled by default.
Recommendations
Researchers at cybersecurity company watchTowr recommend that affected users patch the vulnerability immediately or disable HTTP/2 until a proper solution is implemented. The Apache Software Foundation has also released additional patches for two other vulnerabilities: CVE-2026-106023 (null pointer dereference in 'mod_md') and CVE-2026-109163 (data overwrite flaw in 'mod_vhost_alias').
Additional Context
The Apache HTTP Server is estimated to back roughly one out of five websites, making it a critical target for attackers. The vulnerability was discovered by Anthropic’s OSS Scanner and Google Cloud’s Vulnerability Research teams. The Apache Software Foundation has acknowledged the severity of the issue and has provided a timeline for the release of the patches.
Conclusion
Apache HTTP Server has released critical security updates to address a race condition vulnerability in the mod_http2 module, which could allow attackers to execute arbitrary code with server privileges. Users are advised to patch the vulnerability immediately or disable HTTP/2 until a proper solution is implemented. The Apache Software Foundation has provided additional patches for two other vulnerabilities, and users are encouraged to apply these updates as well. This vulnerability underscores the importance of keeping software up-to-date and secure, especially for widely used open-source tools like Apache HTTP Server.
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