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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-84429?
How do I fix CVE-2026-84429?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-84429 being exploited?
There is no known exploitation of CVE-2026-84429 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-84429, GHSA-76g2-x83x-73r7, UBUNTU-CVE-2026-84429.