CVE-2026-84382: HTTPX2 Streaming Response Decompression Does Not Vulnerability

HIGH
Advisory Identifier: GHSA-8xx6-hgc6-gc2m
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CVSS 7.5
CWE-409
Published
Advisory Summary

CVE-2026-84382 is a HIGH (CVSS 7.5) streaming response decompression does not vulnerability (CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)) affecting HTTPX2 libraries in the PyPI ecosystem. The issue involves streaming response decompression does not bound peak memory (decompression amplification). Remediation is available by upgrading affected packages to version 2.12.0.

CVE-2026-84382 at a Glance

CVE Identifier CVE-2026-84382
GHSA Identifier GHSA-8xx6-hgc6-gc2m
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-409: Improper Handling of Highly Compressed Data (Data Amplification)
Affected Product HTTPX2
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2026-84382

To remediate this vulnerability, upgrade all affected HTTPX2 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

httpx2 fixed: 2.12.0 
pip install httpx2>=2.12.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show httpx2

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-84382, inspect your installed packages using pip:

pip show httpx2

Analyze the terminal output to locate any version of HTTPX2 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.12.0), your application is affected.

Note: The pip show httpx2 command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-409: Improper Handling of Highly Compressed Data (Data Amplification), where the product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output. In HTTPX2, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary When decoding a compressed response body (`gzip`, `deflate`, `br`, or `zstd`), HTTPX2 fully decompressed each network read before yielding content to the application. A small compressed input could therefore cause a large intermediate memory allocation, even when the application streamed the response to keep memory usage bounded. ### Details HTTPX2's default transport reads the socket in pieces of up to 64 KiB. Before `2.12.0`, each piece was inflated completely into one intermediate allocation before any decompressed bytes were yielded. At DEFLATE's maximum compression ratio of roughly 1032:1, a 64 KiB compressed chunk can expand to about 64 MiB in one allocation. Brotli and Zstandard responses can cause similarly large amplification. Streaming the response did not prevent these transient allocations. ### Impact Applications that fetch resources from untrusted or attacker-influenced servers - such as webhook receivers, link unfurlers, crawlers, SSRF-reachable fetchers, and redirect followers - can experience memory pressure or out-of-memory termination when processing a malicious compressed response. No authentication or user interaction is required beyond issuing a request to the server. ### Mitigation Upgrade to HTTPX2 `2.12.0` or later. Patched versions decompress responses incrementally with bounded intermediate buffers, including responses with multiple content encodings.

CVE-2026-84382 Affected HTTPX2 Versions

1 component(s)
Fixed Versions:
2.12.0
Product / Package Ecosystem Affected Versions Fixed Version
httpx2
pypi/httpx2
PyPI
< 2.12.0
2.12.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/pydantic/httpx2/security/advisories/GHSA-8xx6-hgc6-gc2m
NVD — CVE-2026-84382 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-84382
HTTPX2 Source Repository REPOSITORY
https://github.com/pydantic/httpx2/pull/1126
Security Fix Commit FIX COMMIT
https://github.com/pydantic/httpx2/commit/4fd0c70a3f207c618b145934792f791bccfb39f8
HTTPX2 Source Repository REPOSITORY
https://github.com/pydantic/httpx2
HTTPX2 Release RELEASE
https://github.com/pydantic/httpx2/releases/tag/v2.12.0

Frequently Asked Questions

What is CVE-2026-84382?
CVE-2026-84382 is a security vulnerability in HTTPX2 involving Streaming response decompression does not bound peak memory (decompression amplification) under CWE-409: Improper Handling of Highly Compressed Data (Data Amplification).
Which HTTPX2 versions are affected?
Affected versions include releases prior to 2.12.0 across affected packages: httpx2.
What version fixes CVE-2026-84382?
Upgrading to 2.12.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is httpx2 affected?
Yes, httpx2 is affected in releases prior to 2.12.0. Upgrade your dependency to 2.12.0 or later.
What is the CVSS score of CVE-2026-84382?
CVE-2026-84382 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2026-84382?
CVE-2026-84382 is classified under CWE-409: Improper Handling of Highly Compressed Data (Data Amplification) (The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.).
How can I check PyPI dependencies for CVE-2026-84382?
Run the dependency tree command: 'pip show httpx2'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
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  "id" : "GHSA-8xx6-hgc6-gc2m",
  "modified" : "2026-09-08T20:48:59Z",
  "published" : "2026-09-08T20:48:59Z",
  "aliases" : [ "CVE-2026-84382" ],
  "summary" : "HTTPX2: Streaming response decompression does not bound peak memory (decompression amplification)",
  "details" : "### Summary\n\nWhen decoding a compressed response body (`gzip`, `deflate`, `br`, or `zstd`), HTTPX2 fully decompressed each network read before yielding content to the application. A small compressed input could therefore cause a large intermediate memory allocation, even when the application streamed the response to keep memory usage bounded.\n\n### Details\n\nHTTPX2's default transport reads the socket in pieces of up to 64 KiB. Before `2.12.0`, each piece was inflated completely into one intermediate allocation before any decompressed bytes were yielded.\n\nAt DEFLATE's maximum compression ratio of roughly 1032:1, a 64 KiB compressed chunk can expand to about 64 MiB in one allocation. Brotli and Zstandard responses can cause similarly large amplification. Streaming the response did not prevent these transient allocations.\n\n### Impact\n\nApplications that fetch resources from untrusted or attacker-influenced servers - such as webhook receivers, link unfurlers, crawlers, SSRF-reachable fetchers, and redirect followers - can experience memory pressure or out-of-memory termination when processing a malicious compressed response. No authentication or user interaction is required beyond issuing a request to the server.\n\n### Mitigation\n\nUpgrade to HTTPX2 `2.12.0` or later. Patched versions decompress responses incrementally with bounded intermediate buffers, including responses with multiple content encodings.",
  "severity" : [ {
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  "database_specific" : {
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    "nvd_published_at" : "2026-09-02T19:18:08Z"
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}