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CVE-2026-44453

7.5 · HIGH

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3.

Published Jul 16, 2026CWE-770EPSS 0.49%

Overview

CVE-2026-44453 is a high-severity vulnerability. It was published on July 16, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 6b5370d, h2o is vulnerable to a Denial of Service attack when calling alloca under certain conditions. When serving static files, h2o builds the file path on stack, by calling alloca. The maximum size of the memory allocated using alloca can be as huge as ~600KB, which exceeds the default pthread stack size used by musl libc (128KB). If the amount of memory allocated by alloca exceeds the stack size, the h2o server crashes with a segmentation fault, while it tries to touch the guard page. This issue has been fixed by commit 6b5370d.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/h2o/h2o/commit/6b5370d9d09fcf83aa7620ddf77de1954a192181GitHubgithub.com/h2o/h2o/security/advisories/GHSA-rf9v-m59p-mq84

How CyberStrike helps

Frequently asked questions

What is CVE-2026-44453?

CVE-2026-44453 is a high-severity vulnerability. It was published on July 16, 2026 and has a CVSS 3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-44453?

This vulnerability has a CVSS 3.1 base score of 7.5, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-44453?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-44453?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-44453 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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