Brotli versions up to 1.1.0 are vulnerable to a denial of service (DoS) attack due to decompression. This issue has been patched in Brotli version 1.2.0.

Additionally, this affects users who implement the Brotli decompression with Scrapy versions up to 2.13.2, leaving them vulnerable to a denial of service (DoS) attack. The protection mechanism against decompression bombs fails to mitigate the brotli variant, allowing remote servers to crash clients with less than 80GB of available memory. This occurs because brotli can achieve extremely high compression ratios for zero-filled data, leading to excessive memory consumption during decompression.

Impact

If you use HttpAuthMiddleware (i.e. the httpuser and httppass spider attributes) for HTTP authentication, all requests will expose your credentials to the request target.

This includes requests generated by Scrapy components, such as robots.txt requests sent by Scrapy when the ROBOTSTXTOBEY setting is set to True, or as requests reached through redirects.

Patches

Upgrade to Scrapy 2.5.1 and use the new httpauthdomain spider attribute to control which domains are allowed to receive the configured HTTP authentication credentials.

If you are using Scrapy 1.8 or a lower version, and upgrading to Scrapy 2.5.1 is not an option, you may upgrade to Scrapy 1.8.1 instead.

Workarounds

If you cannot upgrade, set your HTTP authentication credentials on a per-request basis, using for example the w3lib.http.basicauthheader function to convert your credentials into a value that you can assign to the Authorization header of your request, instead of defining your credentials globally using HttpAuthMiddleware.

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