EUVD-2026-70248Severity by source
AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
Request smuggling enables cross-user session impact warranting S:C; no meaningful availability impact; AC:H reflects mandatory conflicting-proxy-interpretation prerequisite.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
4DescriptionCVE.org
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.
AnalysisAI
HTTP request smuggling in pydantic's HTTPX2 Python client library, all versions prior to 2.11.0, arises because Request._prepare() in _models.py appends a Content-Length header even when a caller-supplied Transfer-Encoding header is already present, producing HTTP/1.1 requests with two conflicting framing headers simultaneously. Downstream intermediaries such as reverse proxies or API gateways that resolve the Content-Length vs. …
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Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires: (1) the application uses HTTPX2 prior to version 2.11.0 as an HTTP/1.1 client; (2) application code explicitly sets a Transfer-Encoding header on a request that also carries a fixed-size body (byte literals, JSON, form data, or known-length multipart) - default HTTPX2 usage that does not manually inject this header is unaffected; (3) the request traverses at least one HTTP intermediary-reverse proxy, CDN edge, or API gateway-whose Transfer-Encoding vs. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 5.6 score with AV:N/AC:H reflects a genuine exploitation barrier: a specific type of intermediary-one that resolves the Content-Length vs. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade HTTPX2 to version 2.11.0, the vendor-released patched version available at https://github.com/pydantic/httpx2/releases/tag/v2.11.0. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-444 – HTTP Request/Response Smuggling
View allSame technique Request Smuggling
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External POC / Exploit Code
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