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DjangoFramework / library · Djangoproject

CVE-2025-27556

HIGH · 7.5 CVSS v3.1 Published 2025-04-02
Fix available
A fix is available. Upgrade to 5.0.14 / 5.1.8 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
An issue was discovered in Django 5.1 before 5.1.8 and 5.0 before 5.0.14. The NFKC normalization is slow on Windows. As a consequence, django.contrib.auth.views.LoginView, django.contrib.auth.views.LogoutView, and django.views.i18n.set_language are subject to a potential denial-of-service attack via certain inputs with a very large number of Unicode characters.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Django's NFKC Unicode normalization is excessively slow on Windows, and three authentication/i18n views (LoginView, LogoutView, set_language) do not limit Unicode input size. Attackers can submit inputs containing very large numbers of Unicode characters, causing the NFKC normalization to consume excessive CPU and result in denial of service.

MitigationUpgrade Django to version 5.1.8, 5.0.14, or later. Alternatively, implement input validation to restrict the maximum number of Unicode characters accepted by the affected views.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
DjangoFramework / library
Affected:>= 5.0, < 5.0.14>= 5.1, < 5.1.8

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Django version
    Run 'django-admin --version' or in Python: import django; print(django.get_version())
    Affected if Version is 5.0.x where x < 14, or 5.1.x where x < 8 (i.e., falls within 5.0 to <5.0.14 or 5.1 to <5.1.8)
  2. Confirm Windows platform
    Run 'python -c "import platform; print(platform.system())"'
    Affected if Operating system is Windows (the NFKC normalization slowness is specific to Windows)
  3. Identify exposed vulnerable views
    Inspect your URL configuration (urls.py) and check if django.contrib.auth.views.LoginView, LogoutView, or django.views.i18n.set_language are routed and publicly accessible
    Affected if Any of these three views (LoginView, LogoutView, set_language) are exposed without authentication or rate limiting
  4. Check for Unicode input length limits
    Examine the form classes or view logic handling user input for these views (e.g., username field in login forms, language parameter in set_language). Look for max_length, validators, or custom length checks on text inputs
    Affected if No character length limit or validation is enforced on Unicode text inputs submitted to these views

Environment is affected if running a vulnerable Django version (5.0.x < 5.0.14 or 5.1.x < 5.1.8) on Windows with LoginView, LogoutView, or set_language views exposed and lacking input size restrictions on Unicode fields

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.0.14 / 5.1.8 or later
Fixed in 5.0.145.1.8
Interim mitigation

Upgrade Django to version 5.1.8, 5.0.14, or later. Alternatively, implement input validation to restrict the maximum number of Unicode characters accepted by the affected views.

Recommended fix High confidence

Django 5.0.14 or 5.1.8

  1. Check the current Django version in your project by running `python -m django --version`
  2. Update your requirements file (requirements.txt, pyproject.toml, or similar) to specify Django 5.0.14 or 5.1.8 (e.g., `Django>=5.0.14,<5.1.0` or `Django>=5.1.8`)
  3. Run `pip install -U Django` or `pip install Django==5.0.14` (or 5.1.8) to install the fixed version
  4. Verify the installation by running `python -m django --version`
  5. Run your project's test suite to ensure the upgrade does not break existing functionality
  6. Deploy the updated version to your production environment
Caveat Django patch releases generally contain only bug fixes and security patches with no expected breaking changes; however, always run tests before deploying to production

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Django Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-27556 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data