sanic chunked trailer request smuggling allows hidden second request execution

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

EPSS

• CVE-2026-85078: 0.51% estimated exploitation activity in the next 30 days; percentile 43.63 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Description Sanic's HTTP/1.1 chunked-body handling does not fully consume the trailer-part after the terminating 0\r\n chunk. Because of that, attacker-controlled bytes left in the connection buffer after the first chunked request can be interpreted as the start of a new HTTP request on the same keep-alive connection. In the attached verified proof, a single outer POST / request that correctly returns 405 Method Not Allowed is followed, within the same TCP send, by a hidden second request smuggled through the chunked trailer area. Sanic parses and executes that second request as a real independent request. The issue is a request-boundary integrity failure in Sanic's core HTTP/1.1 parser. The verified impact is not speculative. The attached proof shows that one TCP payload produces two server responses: first the expected 405 for the outer POST /, then a separate 200 OK for a hidden GET /. A second exploit variant changes the hidden request path and receives a real 404 Not Found,…

Published by the source

17 Sep 2026, 14:59 UTC

Last modified by the source

1 Oct 2026, 17:56 UTC

Source last checked

26 Oct 2026, 13:52 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-wmj6-g64g-j7q5

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-wmj6-g64g-j7q5

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-wmj6-g64g-j7q5

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# Patch Next advisory brief: CVE-2026-85078

Advisory: sanic chunked trailer request smuggling allows hidden second request execution
IDs: CVE-2026-85078, GHSA-wmj6-g64g-j7q5
Record: https://patchnext.com/advisories/cve-2026-85078 (revision 3, source checked 26 Oct 2026, 13:52 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: sanic 25.12.1, 24.12.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI sanic: affected < 24.12.1; >= 25.12.0, < 25.12.1; fixed in 24.12.1, 25.12.1

## Suggested inspection (read-only)
- `python -m pip show sanic`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on sanic.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-wmj6-g64g-j7q5 (GitHub-reviewed advisory GHSA-wmj6-g64g-j7q5 lists affected ranges: PyPI sanic >=0 =25.12.0 <25.12.1)
- Verified: https://osv.dev/vulnerability/GHSA-wmj6-g64g-j7q5 (OSV record GHSA-wmj6-g64g-j7q5 lists affected ranges: PyPI sanic >=0 =25.12.0 <25.12.1 (fixed))

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