CVE-2026-84382 is a high-severity (CVSS 7.5) CWE-409 vulnerability in httpx2. A fix is available for httpx2 — see the affected versions and patch details below.
HTTPX2: Streaming response decompression does not bound peak memory (decompression amplification)
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-84382.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-84382 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 390,807 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
httpx2Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | httpx2 | all versions | 2.12.0pip install --upgrade 'httpx2==2.12.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for httpx2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update httpx2 to 2.12.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-84382 is resolved across your whole dependency graph.
Workarounds
Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat AI Inference Server 3.5 | rhaii/vllm-rocm-rhel9:1791425869 | RHSA-2026:82059 |
| Red Hat AI Inference Server 3.5 | rhaii/vllm-gaudi-rhel9:1791427182 | RHSA-2026:82061 |
| Red Hat AI Inference Server 3.5 | rhaii/vllm-cuda-rhel9:1791473631 | RHSA-2026:82368 |
| Red Hat AI Inference Server 3.5 | rhaii/vllm-spyre-rhel9:1791818357 | RHSA-2026:82371 |
| Red Hat AI Inference Server 3.5 | rhaii/vllm-cpu-rhel9:1791473614 | RHSA-2026:82415 |
Frequently Asked Questions
Is CVE-2026-84382 in your dependencies?
Find it across PyPI, including transitive dependencies.