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CVE-2026-69243 is a medium-severity HTTP request smuggling vulnerability affecting the AIOHTTP asynchronous HTTP client/server framework for Python. The flaw resides in the HTTP parser’s handling of WebSocket upgrade requests. Prior to version 3.14.2, the parser could be tricked into switching protocols before fully consuming the request body.
In a typical HTTP-to-WebSocket upgrade, the client sends an HTTP GET request with `Connection: Upgrade` and `Upgrade: websocket` headers, along with a `Sec-WebSocket-Key` and other handshake details. The server, upon validating the upgrade, responds with a `101 Switching Protocols` status and then both parties switch to the WebSocket protocol. The vulnerability arises when an attacker crafts a WebSocket upgrade request that also includes a request body.
The AIOHTTP parser, upon detecting a valid WebSocket upgrade, would switch to the WebSocket protocol state immediately after parsing the headers, without waiting for the complete request body to be read. Any bytes remaining in the TCP stream—intended as the request body—were then misinterpreted as either WebSocket protocol data or as a pipelined HTTP request. This parsing differential is the core of the smuggling technique.
An attacker can exploit this by sending a single HTTP request that contains two requests concatenated: the first is a WebSocket upgrade with a body that contains the second, smuggled HTTP request. The parser processes the upgrade, switches protocols, and leaves the trailing bytes (the smuggled request) to be handled as a new HTTP request on the same connection. This can lead to request queue poisoning, cache poisoning, or bypass of security controls.
The vulnerability requires a server-side component of AIOHTTP that handles WebSocket upgrades. It is network-accessible, requires no privileges, and no user interaction. The attack complexity is considered HIGH due to the specific conditions needed to trigger the parser differential. The impact is limited to integrity (low) with no impact on confidentiality or availability. The issue is fixed in AIOHTTP version 3.14.2.
DailyCVE Form:
Platform: aiohttp
Version: <3.14.2
Vulnerability: HTTP Request Smuggling
Severity: Medium (CVSS 6.3)
date: 2026-08-03
Prediction: 2026-08-03 (v3.14.2)
What Undercode Say:
Analytics: The vulnerability affects all AIOHTTP servers prior to 3.14.2 that support WebSocket upgrades. The attack vector is NETWORK, with HIGH attack complexity. No privileges or user interaction are required. The CVSS v4.0 base score is 6.3, with a MEDIUM severity rating. The weakness is classified as CWE-444: Inconsistent Interpretation of HTTP Requests (‘HTTP Request/Response Smuggling’). The patch commit is aio-libs/aiohttp@6ae358f. The vulnerability was published to the GitHub Advisory Database on August 3, 2026.
Bash commands and codes to verify and remediate:
Check installed version pip show aiohttp | grep Version Upgrade to patched version pip install --upgrade aiohttp>=3.14.2 Verify upgrade python -c "import aiohttp; print(aiohttp.<strong>version</strong>)"
Example of a vulnerable server (do not use in production)
from aiohttp import web
async def websocket_handler(request):
ws = web.WebSocketResponse()
await ws.prepare(request)
... handle WebSocket
return ws
app = web.Application()
app.router.add_get('/ws', websocket_handler)
web.run_app(app)
Exploit:
A proof-of-concept exploit would involve crafting an HTTP request that combines a WebSocket upgrade with a smuggled second request. The attacker sends a request like:
GET /ws HTTP/1.1 Host: target.com Connection: Upgrade Upgrade: websocket Sec-WebSocket-Key: x3JJHMbDL1EzLkh9GBhXDw== Sec-WebSocket-Version: 13 Content-Length: 40 GET /admin HTTP/1.1 Host: target.com
The parser sees the WebSocket upgrade, switches protocols, and the remaining bytes (GET /admin...) are treated as a new HTTP request on the same connection, potentially accessing restricted endpoints. The smuggled request can be crafted to bypass authentication, poison caches, or perform other malicious actions.
Protection:
- Immediate: Upgrade AIOHTTP to version 3.14.2 or later.
- Workaround: If immediate upgrade is not possible, disable WebSocket endpoints or implement a reverse proxy that validates WebSocket upgrade requests and rejects any with a request body.
- Network: Deploy a Web Application Firewall (WAF) with rules to detect and block request smuggling patterns.
- Monitoring: Monitor logs for unusual WebSocket upgrade requests with non-zero content length.
- Code Review: Ensure that any custom HTTP parser logic correctly handles protocol switching only after the full request body is consumed.
Impact:
- Request Smuggling: An attacker can smuggle malicious HTTP requests through the server, potentially bypassing security controls, accessing restricted resources, or poisoning caches.
- Integrity Impact: LOW – the attacker can modify the interpretation of HTTP requests, leading to potential data corruption or unauthorized actions.
- Confidentiality: NONE – no direct data exposure.
- Availability: NONE – no direct denial-of-service impact.
- Business Impact: Depending on the application, this could lead to privilege escalation, data leakage via cache poisoning, or cross-user request manipulation. The vulnerability is especially dangerous in multi-tenant environments or where the server sits behind a proxy that may have different parsing rules.
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Sources:
Reported By: github.com
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