# CVE-2026-121441: Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 wasi-http Request Smuggling

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 contains a request smuggling vulnerability in wasi-http that allows guests to set multiple conflicting content-length headers. Malicious guests can make the host send HTTP requests with conflicting content-length values to smuggle requests through servers or intermediaries that do not reject them.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- bytecodealliance / wasmtime (wasmtime-wasi-http): ≥ 0; < 36.0.19 (affected, semver); 36.0.19 (unaffected, semver); ≥ 37.0.0; < 48.0.7 (affected, semver); 48.0.7 (unaffected, semver); ≥ 49.0.0; < 49.0.4 (affected, semver); 49.0.4 (unaffected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); 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; source: CNA: VulnCheck

- CVSS 3.1: 3.7 (low); CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-444

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-r8xh-cgf7-392j (CNA: VulnCheck; vendor-advisory)

- https://www.vulncheck.com/advisories/wasmtime-before-36.0.19-37.0.0-before-48.0.7-and-49.0.0-before-49.0.4-wasi-http-request-smuggling (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-121441; retrieved 2026-11-03; source updated 2026-11-03

Revision: 5503de2d4b88891dc902ffdaad5bb909f39a32f9d40625cb3d6f9afa107cf41b

Canonical: https://y2.dev/cve/CVE-2026-121441

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