Service interruption via quadratic HTML tag parsing
Published Feb 3, 2026 · Updated Feb 3, 2026
Denial of service in Django 4.2 before 4.2.28, 5.2 before 5.2.11, and 6.0 before 6.0.2 allows remote attackers to interrupt service. TruncateHTMLParser uses deque.remove() on its open-tag stack for every end tag, repeatedly scanning the stack when crafted HTML contains many unmatched end tags. The vulnerable path is reached only when an application applies HTML-aware truncation to attacker-controlled content; quadratic parsing can degrade or halt that application service.
Summary
What happened
Denial of service in Django 4.2 before 4.2.28, 5.2 before 5.2.11, and 6.0 before 6.0.2 allows remote attackers to interrupt service. TruncateHTMLParser uses deque.remove() on its open-tag stack for every end tag, repeatedly scanning the stack when crafted HTML contains many unmatched end tags. The vulnerable path is reached only when an application applies HTML-aware truncation to attacker-controlled content; quadratic parsing can degrade or halt that application service.
The record
- CVE
- CVE-2026-1285
- Published
- Feb 3, 2026
- Updated
- Feb 3, 2026
- Vendor
- Django Software Foundation
- Product
- Django
- Classifications
- CWE-407, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 3, 2026CVE publishedPublication date reported by the CVE source.
- Feb 3, 2026Record 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=4.2 <4.2.28
- Affected versionversion=5.2 <5.2.11
- Affected versionversion=6.0 <6.0.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
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Technologies
Your stack
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Your stack
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