WAF bypass via multiple Content-Type charsets
Published Sep 20, 2022 · Updated Nov 3, 2025
Rule set bypass in OWASP Core Rule Set 3.0.x, 3.1.x, 3.2.1, and 3.3.2 allows remote attackers to evade WAF inspection. The Content-Type checks fail to reject multiple charset parameters, so an encoded payload can pass the configured allow list and reach a backend that decodes it. Exploitation requires such a backend, and the resulting consequence depends on the encoded payload and a separate backend weakness.
Summary
What happened
Rule set bypass in OWASP Core Rule Set 3.0.x, 3.1.x, 3.2.1, and 3.3.2 allows remote attackers to evade WAF inspection. The Content-Type checks fail to reject multiple charset parameters, so an encoded payload can pass the configured allow list and reach a backend that decodes it. Exploitation requires such a backend, and the resulting consequence depends on the encoded payload and a separate backend weakness.
The record
- CVE
- CVE-2022-39955
- Published
- Sep 20, 2022
- Updated
- Nov 3, 2025
- Vendor
- OWASP Foundation
- Product
- OWASP Core Rule Set
- Classifications
- CWE-863, T1027
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 20, 2022CVE publishedPublication date reported by the CVE source.
- Nov 3, 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=3.0.x
- Affected versionversion=3.1.x
- Affected versionversion=unspecified <=3.2.1
- Affected versionversion=unspecified <=3.3.2
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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Public exploit references
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Technologies
Your stack
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Your stack
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