Application header confusion via malformed response acceptance
Published Mar 30, 2025 · Updated Nov 3, 2025
Improper input validation in PHP's HTTP stream wrapper allows remote attackers to cause applications to accept malformed response headers. The wrapper retains lines without a colon, and names containing spaces before a colon, in $http_response_header instead of rejecting the response. The attacker must control an HTTP server fetched through the wrapper; consequences depend on application parsing and include header confusion or request-smuggling behavior.
Summary
What happened
Improper input validation in PHP's HTTP stream wrapper allows remote attackers to cause applications to accept malformed response headers. The wrapper retains lines without a colon, and names containing spaces before a colon, in $http_response_header instead of rejecting the response. The attacker must control an HTTP server fetched through the wrapper; consequences depend on application parsing and include header confusion or request-smuggling behavior.
The record
- CVE
- CVE-2025-1734
- Published
- Mar 30, 2025
- Updated
- Nov 3, 2025
- Vendor
- The PHP Group
- Product
- PHP
- Classifications
- CWE-20
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 30, 2025CVE 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=8.1.* <8.1.32
- Affected versionversion=8.2.* <8.2.28
- Affected versionversion=8.3.* <8.3.19
- Affected versionversion=8.4.* <8.4.5
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
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
- Malformed response-header demonstrationproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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