Django URLParsing NFKC DoS via slow URLField on Windows <6.0.3/5.2.12/4.2.29
CVE-2026-25673 Published on March 3, 2026

Potential denial-of-service vulnerability in URLField via Unicode normalization on Windows
An issue was discovered in 6.0 before 6.0.3, 5.2 before 5.2.12, and 4.2 before 4.2.29. `URLField.to_python()` in Django calls `urllib.parse.urlsplit()`, which performs NFKC normalization on Windows that is disproportionately slow for certain Unicode characters, allowing a remote attacker to cause denial of service via large URL inputs containing these characters. Earlier, unsupported Django series (such as 5.0.x, 4.1.x, and 3.2.x) were not evaluated and may also be affected. Django would like to thank Seokchan Yoon for reporting this issue.

Vendor Advisory Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-25673 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
NONE
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
HIGH

Timeline

Initial report received.

Vulnerability confirmed. 24 days later.

Security release issued. 11 days later.

Weakness Types

What is a Resource Exhaustion Vulnerability?

The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.

CVE-2026-25673 has been classified to as a Resource Exhaustion vulnerability or weakness.

Allocation of Resources Without Limits or Throttling

The software allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor.


Products Associated with CVE-2026-25673

You can be notified by email with stack.watch whenever vulnerabilities like CVE-2026-25673 are published in these products:

Django Project Django
 
Red Hat Ansible Automation Platform
 
Red Hat Discovery
 
Red Hat Satellite
 

Affected Versions

djangoproject Django: Red Hat Ansible Automation Platform 2: Red Hat Discovery 2: Red Hat Satellite 6:

Exploit Probability

EPSS
0.64%
Percentile
45.83%

EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.