ASGI header spoofing via underscore-hyphen conflation
Published Apr 7, 2026 · Updated Apr 7, 2026
Header spoofing in Django ASGIRequest 4.2 before 4.2.30, 5.2 before 5.2.13, and 6.0 before 6.0.4 allows remote attackers to alter trusted headers. ASGIRequest converts hyphens to underscores when building request metadata, so an underscore-bearing name collides with a proxy-filtered hyphenated name instead of being rejected. The request must reach an ASGI deployment behind a proxy that strips the hyphenated security header but accepts its underscore variant; the attacker can then control the application-visible header value.
Summary
What happened
Header spoofing in Django ASGIRequest 4.2 before 4.2.30, 5.2 before 5.2.13, and 6.0 before 6.0.4 allows remote attackers to alter trusted headers. ASGIRequest converts hyphens to underscores when building request metadata, so an underscore-bearing name collides with a proxy-filtered hyphenated name instead of being rejected. The request must reach an ASGI deployment behind a proxy that strips the hyphenated security header but accepts its underscore variant; the attacker can then control the application-visible header value.
The record
- CVE
- CVE-2026-3902
- Published
- Apr 7, 2026
- Updated
- Apr 7, 2026
- Vendor
- Django Software Foundation
- Product
- Django
- Classifications
- CWE-290, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 7, 2026CVE publishedPublication date reported by the CVE source.
- Apr 7, 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 <4.2.30
- Affected versionversion=5.2 <5.2.13
- Affected versionversion=6.0 <6.0.4
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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