CVE-2025-1219: PHP DOM/SimpleXML Charset Vulnerability

CVE-2025-1219 Overview

CVE-2025-1219 is an input validation vulnerability in PHP affecting the DOM and SimpleXML extensions. When requesting an HTTP resource that performs a redirect, the wrong content-type header is used to determine the charset for parsing the returned document. This improper handling can lead to documents being parsed incorrectly or security validations being bypassed, potentially enabling attackers to manipulate how applications process external XML or HTML content.

Critical Impact

Applications using PHP's DOM or SimpleXML extensions to fetch and parse remote resources may incorrectly handle character encoding after redirects, potentially leading to parsing errors or validation bypass that could enable injection attacks.

Affected Products

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

Discovery Timeline

• 2025-03-30 - CVE-2025-1219 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2025-1219

Vulnerability Analysis

This vulnerability stems from improper handling of content-type headers during HTTP redirects in PHP's DOM and SimpleXML extensions. When an application requests an HTTP resource that returns a redirect response (e.g., 301, 302), the extension incorrectly uses the content-type header from the original response rather than the final redirected response to determine the character encoding for parsing.

This behavior can lead to charset mismatches where the document is parsed using an incorrect character encoding. Attackers can exploit this by controlling the redirect chain or the content-type headers returned at different stages of the redirect process.

Root Cause

The root cause is classified under CWE-1116 (Inaccurate Comments), though the practical impact relates to improper state management during HTTP redirect handling. The PHP extensions fail to properly track and update the content-type metadata when following HTTP redirects, instead retaining the charset information from an earlier response in the redirect chain rather than the final response containing the actual document content.

Attack Vector

The vulnerability is exploitable over the network and requires specific conditions to be met. An attacker would need to either:

1. Control an intermediate redirect server that returns a crafted content-type header
2. Manipulate the redirect chain to cause charset confusion between the original and final response

When a PHP application uses DOMDocument::loadHTML(), DOMDocument::load(), or SimpleXML functions to load remote content that performs a redirect, the attacker-controlled charset from the redirect response could override the legitimate charset declaration, causing the final document to be misinterpreted.

This could enable validation bypass scenarios where character encoding tricks are used to smuggle malicious content past security filters, or cause application logic errors due to incorrectly parsed XML/HTML structures.

Detection Methods for CVE-2025-1219

Indicators of Compromise

• Unexpected HTTP redirect chains in application logs when fetching external XML/HTML resources
• Character encoding mismatches or parsing errors in DOM/SimpleXML operations
• Unusual content-type headers in HTTP responses involving redirects
• Application behavior anomalies when processing external resources from untrusted sources

Detection Strategies

• Monitor PHP application logs for DOM or SimpleXML parsing errors that occur after HTTP redirects
• Implement logging around external resource fetching to track redirect chains and content-type headers
• Review application code for usage of DOMDocument::load(), DOMDocument::loadHTML(), or SimpleXML functions with remote URLs
• Deploy web application firewalls to detect unusual redirect patterns or content-type manipulation attempts

Monitoring Recommendations

• Enable verbose logging for PHP DOM and SimpleXML extension operations in development and staging environments
• Monitor for unexpected charset declarations in HTTP responses processed by PHP applications
• Track redirect chains in applications that fetch external resources to identify potential manipulation
• Implement application-level monitoring for XML/HTML parsing anomalies

How to Mitigate CVE-2025-1219

Immediate Actions Required

• Upgrade PHP to version 8.1.32, 8.2.28, 8.3.19, or 8.4.5 depending on your installed branch
• Review applications using DOM or SimpleXML extensions with remote URL loading capabilities
• Consider implementing local content-type validation before parsing fetched resources
• Restrict external resource fetching to trusted sources where possible

Patch Information

PHP has released security patches addressing this vulnerability across all affected version branches. The fix ensures that the correct content-type header from the final response in a redirect chain is used for charset determination. Detailed information is available in the PHP Security Advisory on GitHub.

Additional advisories have been published by Debian LTS and NetApp for their respective distributions.

Workarounds

• Fetch remote content using cURL or other HTTP libraries with explicit charset handling before passing to DOM/SimpleXML
• Explicitly set the encoding when loading documents rather than relying on content-type auto-detection
• Implement application-level validation of content-type headers from final redirect responses
• Avoid loading remote XML/HTML resources from untrusted sources until patches can be applied

# Check current PHP version to determine if upgrade is needed
php -v

# For systems using apt (Debian/Ubuntu), update PHP packages
sudo apt update && sudo apt upgrade php*

# Verify the updated version after patching
php -v | head -1