CVE-2026-23527
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.
Vulnerability Summary
CVSS v3 Score
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:L
EPSS Score (Exploitation Probability)
This vulnerability has a 0.04% probability of being exploited in the next 30 days, ranking higher than 14% of all scored CVEs.
CWE Classification
Related Vulnerabilities
Same Weakness Type(CWE-444)
lighttpd1.4.80 incorrectly merged trailer fields into headers after http request parsing. This behavior can be exploited to conduct HTTP Header Smuggling attacks. Successful exploitation may allow an attacker to: * Bypass access control rules * Inject unsafe input into backend logic that trusts request headers * Execute HTTP Request Smuggling attacks under some conditions This issue affects lighttpd1.4.80
Vulnerability in the Oracle Configurator product of Oracle E-Business Suite (component: Runtime UI). Supported versions that are affected are 12.2.3-12.2.14. Easily exploitable vulnerability allows unauthenticated attacker with network access via HTTP to compromise Oracle Configurator. Successful attacks of this vulnerability can result in unauthorized access to critical data or complete access to all Oracle Configurator accessible data. CVSS 3.1 Base Score 7.5 (Confidentiality impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).
Qlik Sense Enterprise for Windows before August 2023 Patch 2 allows unauthenticated remote code execution, aka QB-21683. Due to improper validation of HTTP headers, a remote attacker is able to elevate their privilege by tunneling HTTP requests, allowing them to execute HTTP requests on the backend server that hosts the repository application. The fixed versions are August 2023 Patch 2, May 2023 Patch 6, February 2023 Patch 10, November 2022 Patch 12, August 2022 Patch 14, May 2022 Patch 16, February 2022 Patch 15, and November 2021 Patch 17. NOTE: this issue exists because of an incomplete fix for CVE-2023-41265.
An HTTP Request Tunneling vulnerability found in Qlik Sense Enterprise for Windows for versions May 2023 Patch 3 and earlier, February 2023 Patch 7 and earlier, November 2022 Patch 10 and earlier, and August 2022 Patch 12 and earlier allows a remote attacker to elevate their privilege by tunneling HTTP requests in the raw HTTP request. This allows them to send requests that get executed by the backend server hosting the repository application. This is fixed in August 2023 IR, May 2023 Patch 4, February 2023 Patch 8, November 2022 Patch 11, and August 2022 Patch 13.
Puma is a Ruby/Rack web server built for parallelism. Prior to versions 6.3.1 and 5.6.7, puma exhibited incorrect behavior when parsing chunked transfer encoding bodies and zero-length Content-Length headers in a way that allowed HTTP request smuggling. Severity of this issue is highly dependent on the nature of the web site using puma is. This could be caused by either incorrect parsing of trailing fields in chunked transfer encoding bodies or by parsing of blank/zero-length Content-Length headers. Both issues have been addressed and this vulnerability has been fixed in versions 6.3.1 and 5.6.7. Users are advised to upgrade. There are no known workarounds for this vulnerability.
Similar SeverityHIGH
Improper link resolution before file access ('link following') in Microsoft Defender allows an authorized attacker to elevate privileges locally.
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.
An Improper Input Validation in Ivanti EPMM before versions 12.6.1.1, 12.7.0.1, and 12.8.0.1 allows a remotely authenticated user with administrative access to achieve remote code execution.
OpenClaw before 2026.4.22 contains a server-side request forgery vulnerability in the Zalo plugin's sendPhoto function that fails to validate outbound photo URLs through the SSRF guard. Attackers can bypass SSRF protection by providing malicious photo URLs to the Zalo Bot API, enabling unauthorized access to internal resources.
OpenClaw before 2026.4.22 contains an exec allowlist analysis vulnerability allowing shell expansion hiding in unquoted heredoc bodies. Attackers can bypass allowlist validation by embedding shell expansion tokens in heredoc bodies to execute unapproved commands at runtime.
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