Is CVE-2026-23527 actively exploited?

No active exploitation of CVE-2026-23527 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-23527 be exploited remotely?

Yes. CVE-2026-23527 is exploitable remotely over the network (CVSS attack vector: Network).

What is the CVSS score of CVE-2026-23527?

CVE-2026-23527 has a CVSS score of 9.8 (CRITICAL).

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CRITICAL

CVE-2026-23527

CWE-444Published: January 15, 2026· Updated: Jun 17, 2026

9.8

CVSS v3.1

Official 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.

NVD Source

Risk Analysis

This critical HTTP Request Smuggling vulnerability in H3, a minimal HTTP framework, arises from a case-sensitive check for the Transfer-Encoding header. With a CVSS score of 9.8, this flaw can lead to severe impacts on confidentiality, integrity, and availability. The absence of an EPSS score and KEV status means its exploitation likelihood is not currently assessed or confirmed in the wild.

No public exploit is currently known for this vulnerability. Its remote exploitability (AV:N) and low attack complexity (AC:L) suggest it could be easily exploited if a proof-of-concept were to emerge.

Recommended Action

Users of H3 should upgrade to version 1.15.5 or later to fix this vulnerability. Ensuring that HTTP parsers adhere strictly to RFC specifications regarding header case-insensitivity is a general hardening measure.

Generated by the CTIWATCH analysis pipeline from this CVE's metadata (CVSS, EPSS, KEV status, exploit intelligence). Verify against vendor advisories before acting.

Technical Analysis

CVE-2026-23527 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 9.8.