CVE-2019-12760

A deserialization vulnerability exists in the way parso through 0.4.0 handles grammar parsing from the cache. Cache loading relies on pickle and, provided that an evil pickle can be written to a cache grammar file and that its parsing can be triggered, this flaw leads to Arbitrary Code Execution. NOTE: This is disputed because the cache directory is not under control of the attacker in any common configuration.

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://gist.github.com/dhondta/f71ae7e5c4234f8edfd2f12503a5dcc7
• https://github.com/davidhalter/parso/issues/75
• https://gist.github.com/dhondta/f71ae7e5c4234f8edfd2f12503a5dcc7
• https://github.com/davidhalter/parso/issues/75