CVE-2018-20718

In Pydio before 8.2.2, an attack is possible via PHP Object Injection because a user is allowed to use the $phpserial$a:0:{} syntax to store a preference. An attacker either needs a public link of a file, or access to any unprivileged user account for creation of such a link.

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://blog.ripstech.com/2018/pydio-unauthenticated-remote-code-execution/
• https://blog.ripstech.com/2018/pydio-unauthenticated-remote-code-execution/