HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated
Priority LOW 25CWE-444Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Impact type
- —
- Confidentiality · integrity · availability
- Low · Low · Low
- Fix status
- Partial Red Hat: 2 fixed, 2 without a fix
Attack profile from CVSS 3.1 · CNA. Fix status from CNA, GitHub and Red Hat.
Summary
HTTPX2 is a next generation HTTP client for Python. Prior to 2.11.0, Request._prepare() in src/httpx2/httpx2/_models.py can add a body-derived Content-Length header to a request that already contains a caller-supplied Transfer-Encoding header because its setdefault() processing checks each default header independently rather than treating the two framing headers as mutually exclusive. Fixed-size byte, JSON, form, and known-length multipart bodies can therefore be serialized over HTTP/1.1 with both headers, allowing request smuggling or connection desynchronization when downstream intermediaries disagree about which framing header takes precedence. This issue is fixed in version 2.11.0.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00221 12th percentileScored 2026-11-07
Fix Partial httpx2 (pydantic): 2.11.0httpx2 (PyPI): 2.11.0Red Hat: 7 advisoriesRed Hat: 2 fixed, 2 without a fix
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| pydantic | httpx2 | before 2.11.0 | 2.11.0 | Patch available | CNA |
| — | httpx2 (PyPI) | before 2.11.0 | 2.11.0 | Patch available | GHSA-pf96-p4fj-6566 |
- httpx2 Vendorpydantic Affected before 2.11.0 Fixed in 2.11.0 Patch available CNA
- httpx2 (PyPI) Vendor— Affected before 2.11.0 Fixed in 2.11.0 Patch available GHSA-pf96-p4fj-6566
Remediation
- Fix · CNA httpx2 (pydantic) Fixed in 2.11.0
- Fix · GHSA-pf96-p4fj-6566 httpx2 (PyPI) Fixed in 2.11.0 Advisory →
Red Hat 7 advisories
- RHSA-2026:92452 Released 2026-10-29 · Red Hat rating CriticalRed Hat Enterprise Linux AI 3.5.2 enhancement update
- Red Hat Enterprise Linux AI 3.5 registry.redhat.io/rhelai3/bootc-aws-cuda-rhel9, registry.redhat.io/rhelai3/bootc-azure-cuda-rhel9, registry.redhat.io/rhelai3/bootc-azure-rocm-rhel9 +3
- RHSA-2026:92449 Released 2026-10-29 · Red Hat rating CriticalRed Hat Enterprise Linux AI 3.5.2 enhancement update
- Red Hat Enterprise Linux AI 3.5 registry.redhat.io/rhelai3/disk-image-cuda-rhel9
- RHSA-2026:82415 Released 2026-10-13 · Red Hat rating CriticalRed Hat AI Inference 3.5.2 (cpu)
- Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-cpu-rhel9
Show 4 more Red Hat advisories
- RHSA-2026:82371 Released 2026-10-13 · Red Hat rating CriticalRed Hat AI Inference 3.5.2 (spyre)
- Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-spyre-rhel9
- RHSA-2026:82368 Released 2026-10-13 · Red Hat rating CriticalRed Hat AI Inference 3.5.2 (cuda)
- Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-cuda-rhel9
- RHSA-2026:82061 Released 2026-10-13 · Red Hat rating CriticalRed Hat AI Inference Tech Preview 3.5.2 (Gaudi)
- Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-gaudi-rhel9
- RHSA-2026:82059 Released 2026-10-13 · Red Hat rating CriticalRed Hat AI Inference 3.5.2 (ROCm)
- Red Hat AI Inference Server 3.5 registry.redhat.io/rhaii/vllm-rocm-rhel9
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Lightspeed Core | Affected | No fix yet: Fix deferred |
| Red Hat OpenShift AI (RHOAI) | Affected | No fix yet: Fix deferred |
| Red Hat AI Inference Server 3.5 | Fixed | RHSA-2026:82059, RHSA-2026:82061, RHSA-2026:82368, RHSA-2026:82371, RHSA-2026:82415 |
| Red Hat Enterprise Linux AI 3.5 | Fixed | RHSA-2026:92449, RHSA-2026:92452 |
Not affected: 2 products
- Migration Toolkit for Applications 8
- Red Hat Enterprise Linux command line assistant
Timeline
- 2026-10-02 Threatist record created from CVE-2026-84380
- 2026-10-03 Alias added: GHSA-pf96-p4fj-6566
- 2026-10-13 Fix available: RHSA-2026:82061 · Red Hat
- 2026-10-13 Fix available: RHSA-2026:82059 · Red Hat
- 2026-10-13 Fix available: Red Hat AI Inference Server 3.5 · Red Hat
- 2026-10-14 Fix available: RHSA-2026:82368 · Red Hat
- 2026-10-14 Fix available: RHSA-2026:82415 · Red Hat
- 2026-10-14 Fix available: RHSA-2026:82371 · Red Hat
- 2026-10-15 Affected versions changed · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92452 · Red Hat
- 2026-10-30 Fix available: RHSA-2026:92449 · Red Hat
- 2026-10-30 Fix available: Red Hat Enterprise Linux AI 3.5 · Red Hat
References
More pydantic vulnerabilities
- TI-2024-03518 Regular expression denial of service in Pydantic < 2.4.0 CVSS 3.1HIGH 7.5
- TI-2026-57990 HTTPX2: Multipart part header injection via unvalidated file Content-Type and custom headers CVSS 3.1MEDIUM 5.3
- TI-2026-41916 Path traversal in pydantic-settings CVSS 3.1MEDIUM 5.3
- TI-2026-20687 Pydantic AI Affected by Server-Side Request Forgery (SSRF) in URL Download Handling CVSS 3.1HIGH 8.6
- TI-2026-57993 HTTPX2: Streaming response decompression does not bound peak memory (decompression amplification) CVSS 3.1HIGH 7.5
- TI-2026-69551 Pydantic AI keeps concurrency slots after streams end early CVSS 3.1HIGH 7.5
Sources
- CVE-2026-84380 · CVE Program
- CVE-2026-84380 · NVD
- FIRST EPSS
- GHSA-pf96-p4fj-6566 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-84380 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences