poc-h2-CVE-2026-71554

CVE-2026-71554 - h2 Duplicate Host Header Request Smuggling Primitive This is my first CVE, and I have released this PoC to document the finding and help others understand and reproduce it. CVE: CVE-2026-71554 GHSA: GHSA-6hr6-w5qg-qmwg Affected: h2 = 4.4.0 Fixed: h2 4.4.1 Severity: Medium CWE-444...

h2: Duplicate Host header could facilitate request smuggling

Impact h2 =4.4.0 accepts request header blocks containing more than one Host header, and forwards every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request carries two Host header lines, which is a request smuggling primitive CWE-444...

GHSA-6HR6-W5QG-QMWG h2: Duplicate Host header could facilitate request smuggling

Impact h2 =4.4.0 accepts request header blocks containing more than one Host header, and forwards every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request carries two Host header lines, which is a request smuggling primitive CWE-444...

CVE-2026-71554

CVE-2026-71554 affects the Python HTTP/2 stack in the h2 package. Versions up to and including 4.4.0 accept header blocks containing more than one Host header and forward all Host headers to the application. When a client downgrades HTTP/2 to HTTP/1.1, this can yield two Host header lines, enabli...

CVE-2026-71554 h2: Duplicate Host header could facilitate request smuggling

h2 is a pure-Python implementation of a HTTP/2 protocol stack. Versions up to and including 4.4.0 accept request header blocks containing more than one Host header, and forward every Host header to the consuming application. Where the consumer downgrades HTTP/2 to HTTP/1.1, the resulting request...

Improper Handling Of Duplicate Host Headers

io.netty, netty-codec-http2 is vulnerable to Improper Handling of Duplicate Host Headers. The vulnerability is due to the HTTP/2-to-HTTP/1.x translation layer failing to deduplicate or validate Host headers when both the :authority pseudo-header and a literal Host header are present, which allows...

OESA-2026-2192 python-aiohttp security update

Async http client/server framework asyncio. Security Fixes: Insufficient restrictions in header/trailer handling could cause uncapped memory usage.CVE-2026-22815 An unbounded DNS cache could result in excessive memory usage possibly resulting in a DoS situation.CVE-2026-34513 An attacker who...

Unity Linux 20.1050e / 20.1060e / 20.1070e Security Update: libsoup (UTSA-2026-014646)

The Unity Linux 20 host has a package installed that is affected by a vulnerability as referenced in the UTSA-2026-014646 advisory. A flaw in libsoups HTTP header handling allows multiple Host: headers in a request and returns the last occurrence for server-side processing. Common front proxies...

AIOHTTP accepts duplicate Host headers

Summary Multiple Host headers were allowed in aiohttp. Impact Mostly this doesn't affect aiohttp security itself, but if a reverse proxy is applying security rules depending on the target Host, it is theoretically possible that the proxy and aiohttp could process different host names, possibly...

GHSA-C427-H43C-VF67 AIOHTTP accepts duplicate Host headers

Summary Multiple Host headers were allowed in aiohttp. Impact Mostly this doesn't affect aiohttp security itself, but if a reverse proxy is applying security rules depending on the target Host, it is theoretically possible that the proxy and aiohttp could process different host names, possibly...

HTTP Request Smuggling

Overview Affected versions of this package are vulnerable to HTTP Request Smuggling via the processing of duplicate Host headers. An attacker can bypass security checks enforced by a reverse proxy by sending requests with multiple Host headers, potentially causing the proxy and the backend to...

CVE-2026-34525

AIOHTTP (async HTTP client/server for asyncio and Python) before version 3.13.4 allowed multiple Host headers due to its header handling. This issue has been fixed in version 3.13.4. Affected component: Host header processing in aiohttp prior to 3.13.4. Remediation: upgrade to 3.13.4 or later. Ex...

CVE-2026-34525 AIOHTTP: Duplicate Host header accepted

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, multiple Host headers were allowed in aiohttp. This issue has been patched in version 3.13.4...

SUSE-SU-2026:20902-1 Security update for libsoup

This update for libsoup fixes the following issues: Update to libsoup 3.6.6: - CVE-2025-12105: heap use-after-free in message queue handling during HTTP/2 read completion bsc1252555. - CVE-2025-14523: Duplicate Host Header Handling Causes Host-Parsing Discrepancy bsc1254876. - CVE-2025-32049:...

OPENSUSE-SU-2026:20384-1 Security update for libsoup

This update for libsoup fixes the following issues: Update to libsoup 3.6.6: - CVE-2025-12105: heap use-after-free in message queue handling during HTTP/2 read completion bsc1252555. - CVE-2025-14523: Duplicate Host Header Handling Causes Host-Parsing Discrepancy bsc1254876. - CVE-2025-32049:...

EulerOS 2.0 SP12 : libsoup (EulerOS-SA-2026-1402)

According to the versions of the libsoup packages installed, the EulerOS installation on the remote host is affected by the following vulnerabilities : A flaw in libsoup's HTTP header handling allows multiple Host: headers in a request and returns the last occurrence for server-side processing...

OPENSUSE-SU-2026:20354-1 Security update for libsoup2

This update for libsoup2 fixes the following issues: - CVE-2025-4476: null pointer dereference may lead to denial of service bsc1243422. - CVE-2025-14523: Duplicate Host Header Handling Causes Host-Parsing Discrepancy bsc1254876. - CVE-2025-32049: Denial of Service attack to websocket server...

OESA-2026-1325 libsoup security update

libsoup is an HTTP client/server library for GNOME. It uses GObjects and the glib main loop, to integrate well with GNOME applications, and also has a synchronous API, for use in threaded applications. Security Fixes: A flaw in libsoup’s HTTP header handling allows multiple Host: headers in a...

OESA-2026-1324 libsoup security update

libsoup is an HTTP client/server library for GNOME. It uses GObjects and the glib main loop, to integrate well with GNOME applications, and also has a synchronous API, for use in threaded applications. Security Fixes: A flaw in libsoup’s HTTP header handling allows multiple Host: headers in a...

OESA-2026-1326 libsoup security update

libsoup is an HTTP client/server library for GNOME. It uses GObjects and the glib main loop, to integrate well with GNOME applications, and also has a synchronous API, for use in threaded applications. Security Fixes: A flaw in libsoup’s HTTP header handling allows multiple Host: headers in a...