CVE-2026-126406

EUVD-2026-125159

13.11.2026, 10:17

The wasmtime-wasi-http p2 implementation in Wasmtime before 36.0.20, 37.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 can send conflicting content-length headers, or ones not matching the body, in outgoing requests. A guest that reuses a received response's headers resource to send a bodyless request can enable request smuggling against non-compliant servers, potentially bypassing embedder destination access controls.

HTTP Request/Response Smuggling

Provider	Type	Base Score	Atk. Vector	Atk. Complexity	Priv. Required	Vector
VulnCheck	CNA	3.7 LOW	NETWORK	HIGH	NONE	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Base Score

CVSS 3.x

EPSS Score

Percentile: 25.17%

Early Detection

Affected products identified ahead of NVD analysis through intelligence sources (CNA/ADP records, vendor advisories, Enginsight analysis).

Vendor	Product	Version	Source
bytecodealliance	wasmtime	𝑥 < 36.0.20	CNA
bytecodealliance	wasmtime	37.0.0 ≤ 𝑥 < 48.0.8	CNA
bytecodealliance	wasmtime	49.0.0 ≤ 𝑥 < 49.0.5	CNA
bytecodealliance	wasmtime	50.0.0 ≤ 𝑥 < 50.0.1	CNA

Ubuntu Releases

Ubuntu Product

Codename

rust-wasmtime

jammy	dne
noble	needs-triage
resolute	needs-triage
stonking	needs-triage

Common Weakness Enumeration

CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
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.

References

https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-h4wp-g4x3-7398

https://www.vulncheck.com/advisories/wasmtime-before-36.0.20-http-request-smuggling-via-wasi-http-p2-content-length