CVE-2026-126406

Description

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.

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

• 6.3CVSS 4.0, Mediumfrom the CNA (VulnCheck)CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
• 3.7CVSS 3.1, Lowfrom the CNA (VulnCheck)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

No explicit remediation statement is available on this page yet. Consult the original record and vendor references before choosing a fix.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Timeline

1. 13 Nov 2026 Published

Weakness

• CWE-444

References

• GitHub Security Advisory (GHSA-h4wp-g4x3-7398)vendor-advisory
• VulnCheck Advisory: Wasmtime before 36.0.20 HTTP Request Smuggling via wasi-http p2 Content-Lengththird-party-advisory