CVE-2020-36326

PHPMailer 6.1.8 through 6.4.0 allows object injection through Phar Deserialization via addAttachment with a UNC pathname. NOTE: this is similar to CVE-2018-19296, but arose because 6.1.8 fixed a functionality problem in which UNC pathnames were always considered unreadable by PHPMailer, even in safe contexts. As an unintended side effect, this fix eliminated the code that blocked addAttachment exploitation.

Weakness

The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

Affected Software

Potential Mitigations

• Make fields transient to protect them from deserialization.
• An attempt to serialize and then deserialize a class containing transient fields will result in NULLs where the transient data should be. This is an excellent way to prevent time, environment-based, or sensitive variables from being carried over and used improperly.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/586.html

References

• https://github.com/PHPMailer/PHPMailer/commit/e2e07a355ee8ff36aba21d0242c5950c56e4c6f9
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3B5WDPGUFNPG4NAZ6G4BZX43BKLAVA5B/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KPU66INRFY5BQ3ESVPRUXJR4DXQAFJVT/
• https://github.com/PHPMailer/PHPMailer/commit/e2e07a355ee8ff36aba21d0242c5950c56e4c6f9
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3B5WDPGUFNPG4NAZ6G4BZX43BKLAVA5B/
• https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/KPU66INRFY5BQ3ESVPRUXJR4DXQAFJVT/