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CVE-2026-23527

8.9 · HIGH

H3 is a minimal H(TTP) framework built for high performance and portability.

Published Jan 15, 2026CWE-444EPSS 0.63%

Overview

CVE-2026-23527 is a high-severity vulnerability. It was published on January 15, 2026 and has a CVSS 3.1 base score of 8.9 (HIGH).

This vulnerability has a CVSS 3.1 base score of 8.9, rated HIGH. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

H3 is a minimal H(TTP) framework built for high performance and portability. Prior to 1.15.5, there is a critical HTTP Request Smuggling vulnerability. readRawBody is doing a strict case-sensitive check for the Transfer-Encoding header. It explicitly looks for "chunked", but per the RFC, this header should be case-insensitive. This vulnerability is fixed in 1.15.5.

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/h3js/h3/commit/618ccf4f37b8b6148bea7f36040471af45bfb097GitHubgithub.com/h3js/h3/releases/tag/v1.15.5GitHubgithub.com/h3js/h3/security/advisories/GHSA-mp2g-9vg9-f4cgRefsimonkoeck.com/writeups/h3-transfer-encoding-request-smuggling

How CyberStrike helps

Frequently asked questions

What is CVE-2026-23527?

CVE-2026-23527 is a high-severity vulnerability. It was published on January 15, 2026 and has a CVSS 3.1 base score of 8.9 (HIGH).

How severe is CVE-2026-23527?

This vulnerability has a CVSS 3.1 base score of 8.9, 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-2026-23527?

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-2026-23527?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-23527 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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