Vulnerability in Bytecodealliance Wasmtime
CVE-2026-121441
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.
Vulnerability class: HTTP Request Smuggling
Published · last modified .
CVSS v3 metric
CVSS v3 base score 3.7 (Low). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/bytecodealliance/wasmtime/security/advisories/GHSA-r8xh-cgf7-392j (vendor-advisory)
- www.vulncheck.com/advisories/wasmtime-before-36.0.19-37.0.0-before-48.0.7-and-4… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-121441?
- CVE-2026-121441 is a low-severity vulnerability in Bytecodealliance Wasmtime, classified under Inconsistent Interpretation of HTTP Requests (HTTP Request/Response Smuggling). CVSS score: 3.7/10. Published 2026-11-03.
- How severe is CVE-2026-121441?
- Low severity. CVSS v3 base score is 3.7 out of 10.