Django 5.x/4.2 DoS via NFKC on Windows (pre5.1.14/4.2.26/5.2.8)
CVE-2025-64458 Published on November 5, 2025
Potential denial-of-service vulnerability in HttpResponseRedirect and HttpResponsePermanentRedirect on Windows
An issue was discovered in 5.1 before 5.1.14, 4.2 before 4.2.26, and 5.2 before 5.2.8.
NFKC normalization in Python is slow on Windows. As a consequence, `django.http.HttpResponseRedirect`, `django.http.HttpResponsePermanentRedirect`, and the shortcut `django.shortcuts.redirect` were subject to a potential denial-of-service attack via certain inputs with a very large number of Unicode 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.
Vulnerability Analysis
CVE-2025-64458 is exploitable 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.
Timeline
Initial report received.
Vulnerability confirmed. 7 days later.
Security release issued. 27 days later.
Weakness Type
Inefficient Algorithmic Complexity
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
Products Associated with CVE-2025-64458
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Affected Versions
djangoproject Django:- Version 5.2 and below 5.2.8 is affected.
- Version 5.2.8 is unaffected.
- Version 5.1 and below 5.1.14 is affected.
- Version 5.1.14 is unaffected.
- Version 4.2 and below 4.2.26 is affected.
- Version 4.2.26 is unaffected.
Exploit Probability
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.