How to Troubleshoot the \'Multiple or Malformed Newlines in additional_header\' Error in PHP\'s mail Function?

Troubleshooting "Multiple or Malformed Newlines in additional_header" Error in PHP Mail Function

The error "Error with PHP mail(): Multiple or malformed newlines found in additional_header" indicates that the script is attempting to send an email with invalid headers. This can occur due to a recent server update or changes in the PHP version.

Causes of the Error

The error arises when the additional_header parameter, which is used to specify additional headers for the email, contains multiple newlines (line breaks). This is considered a security risk because malicious actors could inject newlines into the headers and potentially modify the email content.

Solution

To resolve this error, it is essential to:

• Sanitize headers: Remove multiple newlines from the additional_headers parameter. Valid line breaks include "rn" (carriage return and line feed), but not consecutive newlines (e.g., "nn" or "rr").
• Use additional_headers for headers only: Do not include the email message (body, attachments, etc.) in the additional_headers parameter. This should be placed in the message parameter instead.

Additional Information

This error was introduced due to a security patch in PHP 5.5.26. The patch fixed a vulnerability that allowed malicious actors to inject lines into the email headers, potentially leading to email spoofing and other security concerns.

For more details on this security fix, refer to the following resources:

• [PHP Security Bug Report](https://bugs.php.net/bug.php?id=68776)
• [PHP Git Code Diff](http://git.php.net/?p=php-src.git;a=blobdiff;f=ext/standard/mail.c;h=448013a472a3466245e64b1cb37a9d1b0f7c007e;hp=1ebc8fecb7ef4c266a341cdc701f0686d6482242;hb=9d168b863e007c4e15ebe4d2eecabdf8b0582e30;hpb=eee8b6c33fc968ef8c496db8fb54e8c9d9d5a8f9)

The above is the detailed content of How to Troubleshoot the \'Multiple or Malformed Newlines in additional_header\' Error in PHP\'s mail Function?. For more information, please follow other related articles on the PHP Chinese website!