Django REST framework: Accept header with many large quoted parameters burns ~19s of CPU per request in content negotiation

Exploitation

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

CVSS

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

EPSS

• CVE-2026-114138: 0.60% estimated exploitation activity in the next 30 days; percentile 48.48 (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.

Summary DRF's content negotiation parses each Accept token several times per request and never limits the number of tokens or their total size. Each parse ends up in Django's parseheaderparameters, which takes quadratic time when a quoted parameter value is packed with semicolons. On my machine a single GET with a 780KB Accept header made of 96 such tokens kept one gunicorn worker busy for 18.87 seconds (Django 6.1, djangorestframework 3.18.0, gunicorn 26.0.0, Python 3.13, Docker on macOS). The header is syntactically valid, fits inside gunicorn's default header limits, and needs no authentication. Two concurrent requests, which is one per sync worker, made a default two worker deployment stop answering for my whole 40 second test window. It recovered half a second after I stopped sending. Details What happens getacceptlist() splits the Accept header on commas with no cap on token count or total size, at restframework/negotiation.py:96-97. For every token, selectrenderer() calls…

Published by the source

22 Oct 2026, 16:17 UTC

Last modified by the source

22 Oct 2026, 16:30 UTC

Source last checked

26 Oct 2026, 13:55 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-33wh-fxxf-88vv

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-33wh-fxxf-88vv

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-33wh-fxxf-88vv

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# Patch Next advisory brief: CVE-2026-114138

Advisory: Django REST framework: Accept header with many large quoted parameters burns ~19s of CPU per request in content negotiation
IDs: CVE-2026-114138, GHSA-33wh-fxxf-88vv
Record: https://patchnext.com/advisories/cve-2026-114138 (revision 3, source checked 26 Oct 2026, 13:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: djangorestframework 3.18.2. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI djangorestframework: affected < 3.18.2; fixed in 3.18.2

## Suggested inspection (read-only)
- `python -m pip show djangorestframework`: 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 djangorestframework.
- 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-33wh-fxxf-88vv (GitHub-reviewed advisory GHSA-33wh-fxxf-88vv lists affected ranges: PyPI djangorestframework >=0 <3.18.2)
- Verified: https://osv.dev/vulnerability/GHSA-33wh-fxxf-88vv (OSV record GHSA-33wh-fxxf-88vv lists affected ranges: PyPI djangorestframework >=0 <3.18.2 (fixed))

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