urllib3 2.6.0-<2.7.0 Decompress Whole Response DoS via Brotli
CVE-2026-44432 Published on May 13, 2026
urllib3: Decompression-bomb safeguards bypassed in parts of the streaming API
urllib3 is an HTTP client library for Python. From 2.6.0 to before 2.7.0, urllib3 could decompress the whole response instead of the requested portion (1) during the second HTTPResponse.read(amt=N) call when the response was decompressed using the official Brotli library or (2) when HTTPResponse.drain_conn() was called after the response had been read and decompressed partially (compression algorithm did not matter here). These issues could cause urllib3 to fully decode a small amount of highly compressed data in a single operation. This could result in excessive resource consumption (high CPU usage and massive memory allocation for the decompressed data) on the client side. This vulnerability is fixed in 2.7.0.
Weakness Type
What is a Data Amplification Vulnerability?
The software does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output. An example of data amplification is a "decompression bomb," a small ZIP file that can produce a large amount of data when it is decompressed.
CVE-2026-44432 has been classified to as a Data Amplification vulnerability or weakness.