XXE in petl

Impact

Information Disclosure

Summary

petl is a Python library that provides functions for extraction, transformation, and loading (ETL) of data.

petl before 1.68, in some configurations, allows resolution of entities in XML input.

An attacker who is able to submit XML input to an application using petl can disclose arbitrary files on the file system in the context of the user under which the application is running.

Affected Applications

Applications that:

• accept attacker-supplied XML input that is processed using petl < 1.68
• return the response generated by petl back to the attacker
• configure lxml as the underlying XML processing library used by petl
• have read privileges in filesystem files with sensitive information

Mitigation

Update to petl >= 1.68

Workarounds

• Assure there is no user/external access to the application using petl
• Assure your application is not using the function fromxml()

References

• https://github.com/nvn1729/advisories/blob/master/cve-2020-29128.md
• https://github.com/petl-developers/petl/pull/527
• https://github.com/petl-developers/petl/releases/tag/v1.6.8
• https://petl.readthedocs.io/en/stable/changes.html
• https://owasp.org/www-community/vulnerabilities/XML_External_Entity_(XXE)_Processing

For more information

If you have any questions or comments about this advisory:

• Add a comment in the Github issue

Thaks to Naveen Sunkavally.