Authorization-header suppression via incomplete CRLF validation
Published Mar 30, 2025 · Updated Nov 3, 2025
Header validation flaw in PHP 8.1 before 8.1.32, 8.2 before 8.2.28, 8.3 before 8.3.19, and 8.4 before 8.4.5 allows attackers to suppress HTTP headers. The check_has_header function accepts a line-feed-only boundary without requiring a preceding carriage return, so crafted user-controlled values can masquerade as an Authorization header. Exploitation requires an application to place attacker-influenced data in outbound HTTP headers; the resulting request can omit Basic Authorization or misinterpret other checked headers.
Summary
What happened
Header validation flaw in PHP 8.1 before 8.1.32, 8.2 before 8.2.28, 8.3 before 8.3.19, and 8.4 before 8.4.5 allows attackers to suppress HTTP headers. The check_has_header function accepts a line-feed-only boundary without requiring a preceding carriage return, so crafted user-controlled values can masquerade as an Authorization header. Exploitation requires an application to place attacker-influenced data in outbound HTTP headers; the resulting request can omit Basic Authorization or misinterpret other checked headers.
The record
- CVE
- CVE-2025-1736
- 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
- PHP HTTP-wrapper CRLF regression testsproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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