CVE-2026-84380: medium-severity vulnerability in pydantic httpx2
HTTPX2: Conflicting Content-Length and Transfer-Encoding headers can be auto-generated
Published
E-mail alert when it lands in KEV, gets a public PoC or its score goes up.
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.6epss 0.2%
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.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
Affected products
pydantic · httpx2Related CVEs — pydantic httpx2
In the same product, most dangerous first.
CVE-2026-84382HIGHHTTPX2: Streaming response decompression does not bound peak memory (decompression amplification)EPSS 0.6%CVE-2026-84379MEDIUMHTTPX2: Multipart part header injection via unvalidated file Content-Type and custom headersEPSS 0.3%CVE-2026-84378MEDIUMHTTPX2: Quadratic SSE line buffering can cause CPU denial of serviceEPSS 0.3%CVE-2026-84381HIGHHTTPX2: Secure WebSocket traffic sent without TLS through SOCKS proxiesEPSS 0.1%