CVE-2016-3957

The secure_load function in gluon/utils.py in web2py before 2.14.2 uses pickle.loads to deserialize session information stored in cookies, which might allow remote attackers to execute arbitrary code by leveraging knowledge of encryption_key.

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://devco.re/blog/2017/01/03/web2py-unserialize-code-execution-CVE-2016-3957/
• https://github.com/web2py/web2py/blob/R-2.14.1/gluon/utils.py#L200
• https://usn.ubuntu.com/4030-1/
• https://devco.re/blog/2017/01/03/web2py-unserialize-code-execution-CVE-2016-3957/
• https://github.com/web2py/web2py/blob/R-2.14.1/gluon/utils.py#L200
• https://usn.ubuntu.com/4030-1/