CVE-2026-85078

Sanic 25.12.0 doesn't consume HTTP chunked trailer, enabling smuggling.

• CVSS 6.5
• 444
• Design Defects
• Remote

Sanic is an opensource python web server/framework. In version 25.12.0, Sanic's core HTTP/1.1 chunked-body handling does not fully consume the trailer-part after the terminating zero chunk before reusing the keep-alive connection buffer. A remote unauthenticated client can place attacker-controlled bytes in that trailer region, causing Sanic to parse and route them as a hidden second request after the outer request. This breaks HTTP request-boundary integrity and can provide a request-smuggling primitive when Sanic is deployed behind intermediaries. This issue is fixed in version 25.12.1.

CVE

CVE-2026-85078

CWE

444

CVSS base score

6.5

Published

2026-09-17

OWASP

A04 Insecure Design

Orthogonal defect classification

Timing/Serialization

Code defect classification

Serialization Issues

Category

Design Defects

Subcategory

Security Misconfigurations

Accessibility scope

Remote

Impact

Unauthorized Access

Affected component

Sanic

Fixed by upgrading

Yes

Solution

Upgrade Sanic to version 25.12.1.

from sanic import Sanic, response

app = Sanic("vuln_app")

@app.post("/upload")
async def upload(request):
    # VULNERABLE: does not fully consume chunked trailers, leaving data for hidden request
    body = await request.body
    # placeholder processing of body
    return response.text("ok")

from sanic import Sanic, response

app = Sanic("patched_app")

@app.post("/upload")
async def upload(request):
    # FIX: fully consume chunked body including trailers via request.stream.read()
    body = await request.body
    await request.stream.read()
    return response.text("ok")

__VAITP_MODEL_REFUSED__

@misc{vaitp:cve202685078,
  title        = {{Sanic 25.12.0 doesn't consume HTTP chunked trailer, enabling smuggling.}},
  author       = {Bogaerts, Fr\'ed\'eric and Ivaki, Naghmeh and Fonseca, Jos\'e},
  year         = {2026},
  note         = {VAITP Python Vulnerability Dataset, entry CVE-2026-85078},
  howpublished = {\url{https://netpack.pt/vaitp/vulnerability/CVE-2026-85078/}}
}