Unauthenticated service interruption via Unicode normalization
Published Apr 2, 2025 · Updated Apr 2, 2025
Denial of service in Django 5.1 before 5.1.8 and 5.0 before 5.0.14 allows remote attackers to interrupt Windows services via long URLs. The affected views pass attacker-controlled redirect targets to url_has_allowed_host_and_scheme, whose urlparse call performs slow NFKC normalization without a length limit. Only Windows deployments using LoginView, LogoutView, or set_language are affected; unauthenticated requests containing huge Unicode URL values can consume service capacity.
Summary
What happened
Denial of service in Django 5.1 before 5.1.8 and 5.0 before 5.0.14 allows remote attackers to interrupt Windows services via long URLs. The affected views pass attacker-controlled redirect targets to url_has_allowed_host_and_scheme, whose urlparse call performs slow NFKC normalization without a length limit. Only Windows deployments using LoginView, LogoutView, or set_language are affected; unauthenticated requests containing huge Unicode URL values can consume service capacity.
The record
- CVE
- CVE-2025-27556
- Published
- Apr 2, 2025
- Updated
- Apr 2, 2025
- Vendor
- Django Software Foundation
- Product
- Django
- Classifications
- CWE-770, T1499.003
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 2, 2025CVE publishedPublication date reported by the CVE source.
- Apr 2, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=5.0 <5.0.14
- Affected versionversion=5.1 <5.1.8
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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