CVSS 4.0
6.3 mediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:NCVE-2026-126406 Wasmtime before 36.0.20 HTTP Request Smuggling via wasi-http p2 Content-Length
Medium (6.3) in bytecodealliance wasmtime. EPSS 0.3% estimated probability of exploitation activity in the next 30 days.
On this page
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
CVSS 3.1
3.7 lowCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N- EPSS
- 0.3% estimated probability of exploitation activity in the next 30 days; 25th percentile. Scored 2026-11-13. A forecast for this CVE across the internet, not for your own systems.
- CWE
- CWE-444 Inconsistent Interpretation of HTTP Requests (HTTP Request Smuggling)
- OWASP Top 10
- A06:2025 Insecure Design
- Published
- Modified
- Assigned by
- VulnCheck (CNA)
- NVD analysis
- Deferred: the NVD does not plan to analyze it
- Record from
- the NVD, synced
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Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| bytecodealliance wasmtime | before 36.0.20 |
| bytecodealliance wasmtime | from 37.0.0 before 48.0.8 |
| bytecodealliance wasmtime | from 49.0.0 before 49.0.5 |
| bytecodealliance wasmtime | from 50.0.0 before 50.0.1 |
Linux distributions
| Distribution | Release | Package | Fixed in | Advisory |
|---|---|---|---|---|
| Ubuntu | 24.04:LTS, 26.04:LTS, 26.10 | rust-wasmtime | no fix listed | UBUNTU-CVE-2026-126406 |
From the distributions' data via OSV.dev: Ubuntu Security Notices © Canonical Ltd., CC BY-SA 4.0. Modified: reformatted and linked to CVE records. Credits. On the distributions' own pages: Ubuntu.
Attack patterns (CAPEC)
- CAPEC-33 HTTP Request Smuggling Likelihood: Medium · Severity: High
- CAPEC-273 HTTP Response Smuggling Likelihood: Medium · Severity: High
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits.
History
- The NVD deferred its analysis
Changes since this site first stored the record. The same for every record: /api/public/changes.