CVE-2025-1217: PHP Information Disclosure Vulnerability

CVE-2025-1217 Overview

CVE-2025-1217 is an Improper Input Validation vulnerability affecting PHP's HTTP request module. When parsing HTTP responses obtained from a server, folded headers are processed incorrectly, which may lead to misinterpretation of the response and the use of incorrect headers, MIME types, and other critical response components. This parsing inconsistency represents an HTTP Request Smuggling risk that could be exploited to bypass security controls or manipulate application behavior.

Critical Impact

Incorrect parsing of folded HTTP headers can lead to header injection attacks, MIME type confusion, and potential bypass of security controls in web applications relying on accurate HTTP response parsing.

Affected Products

• PHP versions 8.1.* before 8.1.32
• PHP versions 8.2.* before 8.2.28
• PHP versions 8.3.* before 8.3.19
• PHP versions 8.4.* before 8.4.5

Discovery Timeline

• 2025-03-29 - CVE-2025-1217 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-1217

Vulnerability Analysis

This vulnerability stems from improper handling of folded headers in PHP's HTTP request module. HTTP/1.1 specifications allow headers to span multiple lines when continuation lines begin with whitespace (space or tab characters). PHP's parsing logic fails to correctly process these folded headers, leading to header value misinterpretation.

The vulnerability is classified under CWE-20 (Improper Input Validation) and CWE-436 (Interpretation Conflict), reflecting both the input validation failure and the resulting interpretation discrepancy between PHP and other HTTP parsers. This parsing inconsistency can cause applications to use incorrect header values, potentially affecting content-type handling, authentication mechanisms, and security-sensitive response processing.

Root Cause

The root cause lies in PHP's HTTP response parsing implementation within the HTTP request module. When the parser encounters multi-line (folded) headers where continuation lines are indicated by leading whitespace, it fails to properly concatenate these values according to HTTP specifications. This results in either truncated header values, incorrect header associations, or complete omission of header data.

Attack Vector

The vulnerability is exploitable over the network when PHP applications make HTTP requests to attacker-controlled or compromised servers. An attacker can craft malicious HTTP responses with specially formatted folded headers designed to exploit the parsing inconsistency. Potential attack scenarios include:

1. MIME Type Confusion: Manipulating Content-Type headers to cause PHP to misinterpret response data, potentially leading to security bypasses in content validation
2. Security Header Bypass: Causing security-relevant headers to be parsed incorrectly or ignored entirely
3. Cache Poisoning: Exploiting header misinterpretation to poison caches with malicious content

The vulnerability requires the attacker to control or influence the HTTP response that PHP receives, which limits exploitation scenarios but remains significant for applications interacting with external services.

Detection Methods for CVE-2025-1217

Indicators of Compromise

• Unusual HTTP response parsing errors in PHP application logs
• Unexpected MIME type handling or content-type mismatches in application behavior
• Anomalous header values being processed differently than expected
• Web application firewall logs showing HTTP responses with unusual folded header patterns

Detection Strategies

• Monitor PHP error logs for HTTP parsing warnings or unexpected header handling
• Implement network-level inspection for HTTP responses containing folded headers targeting PHP applications
• Deploy application-level logging to track parsed header values versus raw response data
• Use intrusion detection signatures to identify malformed HTTP responses with suspicious folded header patterns

Monitoring Recommendations

• Enable verbose logging for PHP HTTP request operations to capture parsing anomalies
• Monitor web application traffic for responses containing multi-line headers from untrusted sources
• Implement alerting on Content-Type or security header inconsistencies in PHP applications
• Review application logs for unexpected behavior in MIME type or header-dependent functionality

How to Mitigate CVE-2025-1217

Immediate Actions Required

• Upgrade PHP to patched versions: 8.1.32, 8.2.28, 8.3.19, or 8.4.5 or later
• Review applications that make HTTP requests to external or untrusted services
• Consider implementing application-level header validation as a defense-in-depth measure
• Audit systems to identify all PHP installations requiring updates

Patch Information

PHP has released security updates addressing this vulnerability. Users should upgrade to the following versions:

Additional security advisories are available from PHP Security Advisory on GitHub, Debian LTS Security Announcement, and NetApp Security Advisory.

Workarounds

• Limit PHP applications to communicate only with trusted, known-good HTTP servers where possible
• Implement a reverse proxy or WAF that normalizes HTTP responses before they reach PHP applications
• Add application-level validation of critical headers after parsing to detect inconsistencies
• Consider using alternative HTTP client libraries with independent parsing implementations for critical operations

# Verify PHP version after patching
php -v

# Check for vulnerable PHP versions in common locations
find /usr -name "php" -type f -exec {} -v \; 2>/dev/null | grep -E "PHP 8\.[1-4]\."

# Restart PHP-FPM after upgrade (adjust for your system)
systemctl restart php-fpm