CVE-2020-11467

An issue was discovered in Deskpro before 2019.8.0. This product enables administrators to modify the helpdesk interface by editing /portal/api/style/edit-theme-set/template-sources theme templates, and uses TWIG as its template engine. While direct access to self and _self variables was not permitted, one could abuse the accessible variables in ones context to reach a native unserialize function via the code parameter. There, on could pass a crafted payload to trigger a set of POP gadgets in order to achieve remote code execution.

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.redforce.io/attacking-helpdesks-part-1-rce-chain-on-deskpro/
• https://support.deskpro.com/en/news/posts/deskpro-security-update-2019-09
• https://support.deskpro.com/en/news/posts/deskpro-v2019-8-0-released-security-update
• https://blog.redforce.io/attacking-helpdesks-part-1-rce-chain-on-deskpro/
• https://support.deskpro.com/en/news/posts/deskpro-security-update-2019-09
• https://support.deskpro.com/en/news/posts/deskpro-v2019-8-0-released-security-update