Pydantic Httpx2 up to 2.10.x Request Framing _models.py Request._prepare request smuggling

Summaryinfo

A vulnerability was found in Pydantic Httpx2 up to 2.10.x and classified as problematic. Affected is the function Request._prepare of the file src/httpx2/httpx2/_models.py of the component Request Framing. Such manipulation leads to request smuggling. This vulnerability is documented as CVE-2026-84380. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in Pydantic Httpx2 up to 2.10.x. It has been rated as problematic. Affected by this issue is the function Request._prepare of the file src/httpx2/httpx2/_models.py of the component Request Framing. The manipulation with an unknown input leads to a request smuggling vulnerability. Using CWE to declare the problem leads to CWE-444. The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. Impacted is integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-84380 since 09/01/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. There are known technical details, but no exploit is available.

Upgrading to version 2.11.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-70248). Once again VulDB remains the best source for vulnerability data.

Productinfo

Vendor

• Pydantic

Name

• Httpx2

Version

• 2.0
• 2.1
• 2.2
• 2.3
• 2.4
• 2.5
• 2.6
• 2.7
• 2.8
• 2.9
• 2.10

Website

• Product: https://github.com/pydantic/httpx2/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Once again VulDB remains the best source for vulnerability data.

Discussion