HTTPX2 is a next generation HTTP client for Python. Prior to 2.12.0, the HTTPX2 content decoders in src/httpx2/httpx2/_decoders.py fully inflate each gzip, deflate, br, or zstd network chunk before iter_bytes() or aiter_bytes() yields bounded pieces to the application. A 64 KiB compressed chunk can expand to approximately 64 MiB in one intermediate allocation, so an attacker-controlled or compromised server can cause severe memory pressure or out-of-memory process termination even when the application streams the response. This issue is fixed in version 2.12.0.

CVE-2026-84382 affects HTTPX2, a next-generation HTTP client for Python, in versions prior to 2.12.0. The vulnerability resides in the content decoders within _decoders.py, which fully inflate compressed network chunks (gzip, deflate, br, zstd) before yielding bounded pieces to the application. A 64 KiB compressed chunk can expand to approximately 64 MiB in a single intermediate allocation, leading to severe memory pressure. An attacker-controlled or compromised server can exploit this behavior to cause out-of-memory process termination even when the application uses streaming. The flaw is classified as a resource exhaustion or zip bomb-style vulnerability. The issue has been patched in HTTPX2 version 2.12.0. Users are strongly advised to upgrade to the fixed version immediately.