# CVE-2026-84429: Potential denial-of-service vulnerability in HTTP header parsing

> An unauthenticated attacker can cause a denial of service in Django by sending crafted HTTP headers that trigger quadratic time complexity in header parsing.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Oct 2026
- **Updated:** 6 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-84429, GHSA-76g2-x83x-73r7, UBUNTU-CVE-2026-84429

## What is CVE-2026-84429?

CVE-2026-84429 is a medium-severity denial of service vulnerability in djangoproject Django, published on 6 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in Django 6.1 before 6.1.2, 6.0 before 6.0.9, and 5.2 before 5.2.18.
`django.utils.http.parse_header_parameters()` was subject to a potential denial-of-service attack due to quadratic time complexity when parsing a value with many separators inside a quoted parameter. An unauthenticated request could reach this parsing through headers such as `Accept` or `Content-Type`, for instance via the content negotiation performed by `HttpRequest.accepts()`. The per-call length limit does not bound the combined size of repeated headers.
Earlier, unsupported Django series (such as 5.1.x, 5.0.x, and 4.2.x) were not evaluated and may also be affected.
Django would like to thank Jisung Chae for reporting this issue.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-84429?


## How do I fix CVE-2026-84429?

Upgrade to a fixed version.

## Is CVE-2026-84429 being exploited?

There is no known exploitation of CVE-2026-84429 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84429 and fix it if it is affected.

What it is: CVE-2026-84429 is a medium-severity denial of service vulnerability in djangoproject Django, published on 6 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-84429 in the wild and no public exploit code.

Affected product: djangoproject Django. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-84429/ (Markdown: https://insights.sbomify.com/CVE-2026-84429/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84429
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84429
- OSV: https://osv.dev/vulnerability/CVE-2026-84429

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84429/
Summaries are generated and may contain mistakes; the official description above is the record.