What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-10-06 · updated 2026-10-06
• Weakness: CWE-407

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.

Affected products

• Django: from 6.1 before 6.1.2; from 6.0 before 6.0.9; from 5.2 before 5.2.18 — fixed in 5.2.18, 6.0.9, 6.1.2

How to fix

Upgrade to a fixed version: Django 5.2.18, 6.0.9, 6.1.2. Check the vendor advisory for mitigations.

References

• https://docs.djangoproject.com/en/dev/releases/security/
• https://github.com/django/django/commit/3d8f121695c21234aff3071de0d38b6bd38c3f52
• https://github.com/django/django/commit/6ecd66e09a383be004a78a3a738ea9727ff07b0e
• https://github.com/django/django/commit/7ff7fcc0508864a4bc39693128ace38b1e95a890
• https://github.com/django/django/commit/de56deeabd4c48dfb5193f0001469d80102fb367
• https://groups.google.com/g/django-announce
• https://www.djangoproject.com/weblog/2026/oct/06/security-releases/

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