Scrapy vulnerable to ReDoS via XMLFeedSpider

Impact

The following parts of the Scrapy API were found to be vulnerable to a ReDoS attack:

• The XMLFeedSpider class or any subclass that uses the default node iterator: iternodes, as well as direct uses of the scrapy.utils.iterators.xmliter function.

• Scrapy 2.6.0 to 2.11.0: The open_in_browser function for a response without a base tag.

Handling a malicious response could cause extreme CPU and memory usage during the parsing of its content, due to the use of vulnerable regular expressions for that parsing.

Patches

Upgrade to Scrapy 2.11.1.

If you are using Scrapy 1.8 or a lower version, and upgrading to Scrapy 2.11.1 is not an option, you may upgrade to Scrapy 1.8.4 instead.

Workarounds

For XMLFeedSpider, switch the node iterator to xml or html.

For open_in_browser, before using the function, either manually review the response content to discard a ReDos attack or manually define the base tag to avoid its automatic definition by open_in_browser later.

Acknowledgements

This security issue was reported by @nicecatch2000 through huntr.com.