Impact This is a reintroduction of an earlier issue (CVE-2018-19296) by an unrelated bug fix in PHPMailer 6.1.8. An external file may be unexpectedly executable if it is used as a path to an attachment file via PHP's support for .phar files. Exploitation requires that an attacker is able to provide an unfiltered path to a file to attach, or to trick calling code into generating one. See this article for more info.
Patches This issue was patched in the PHPMailer 6.4.1 release. This release also implements stricter filtering for attachment paths; paths that look like any kind of URL are rejected.
Workarounds Validate paths to loaded files using the same pattern as used in isPermittedPath() before using them in any PHP file function, such as fileexists. This method can't be used directly because it is protected, but you can implement the same thing in calling code. Note that this should be applied to all user-supplied paths passed into such functions; it's not a problem specific to PHPMailer.
Credit This issue was found by Fariskhi Vidyan, reported and managed via Tidelift.
Impact The isMail transport in PHPMailer before 5.2.20 might allow remote attackers to pass extra parameters to the mail command and consequently execute arbitrary code by leveraging improper interaction between the escapeshellarg function and internal escaping performed in the mail function in PHP. NOTE: this vulnerability exists because of an incorrect fix for CVE-2016-10033.
This issue really emphasises that it's worth avoiding the built-in PHP mail() function entirely.
Patches Fixed in 5.2.20
Workarounds Send via SMTP to localhost instead of calling the mail() function.
References https://nvd.nist.gov/vuln/detail/CVE-2016-10045 See also https://nvd.nist.gov/vuln/detail/CVE-2016-10033
For more information If you have any questions or comments about this advisory: Open a private issue in the PHPMailer project
Impact The mailSend function in the default isMail transport in PHPMailer before 5.2.18 might allow remote attackers to pass extra parameters to the mail command and consequently execute arbitrary code via a \" (backslash double quote) in a crafted Sender property.
Patches Fixed in 5.2.18
Workarounds Filter and validate user input before passing it to internal functions.
References https://nvd.nist.gov/vuln/detail/CVE-2016-10033 Related to a follow-on issue in https://nvd.nist.gov/vuln/detail/CVE-2016-10045
For more information If you have any questions or comments about this advisory: Open a private issue in the PHPMailer project