daphne: WebSocket handshake header smuggling through autobahn splitlines() mishandling of non-standard line separators

Exploitation

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

CVSS

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

EPSS

• CVE-2026-44546: 0.17% estimated exploitation activity in the next 30 days; percentile 6.64 (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.

daphne before 4.2.2 reconstructs a raw HTTP request from Twisted's parsed headers and feeds it to autobahn for WebSocket handshake processing. Twisted does not treat \x0b, \x0c, \x1c, \x1d, \x1e, or \x85 as header line separators, but autobahn decodes header values to str and calls splitlines(). An attacker can exploit this parser differential to inject additional headers into the ASGI scope passed to the application. daphne now rejects requests with these bytes in any header value with a 400 response.

Published by the source

3 Jun 2026, 15:30 UTC

Last modified by the source

11 Jul 2026, 23:11 UTC

Source last checked

26 Oct 2026, 13:46 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xh68-hfp5-5x5m

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xh68-hfp5-5x5m

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-44546

Advisory: daphne: WebSocket handshake header smuggling through autobahn splitlines() mishandling of non-standard line separators
IDs: CVE-2026-44546, GHSA-xh68-hfp5-5x5m
Record: https://patchnext.com/advisories/cve-2026-44546 (revision 2, source checked 26 Oct 2026, 13:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 3.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: daphne 4.2.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI daphne: affected < 4.2.2; fixed in 4.2.2

## Suggested inspection (read-only)
- `python -m pip show daphne`: 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 daphne.
- 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://osv.dev/vulnerability/GHSA-xh68-hfp5-5x5m (OSV record GHSA-xh68-hfp5-5x5m lists affected ranges: PyPI daphne >=0 <4.2.2 (fixed))
- Verified: https://github.com/advisories/GHSA-xh68-hfp5-5x5m (GitHub-reviewed advisory GHSA-xh68-hfp5-5x5m lists affected ranges: PyPI daphne >=0 <4.2.2)

Commands are suggestions: review each one before running it.