CVE-2026-121439

EUVD-2026-115861
Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 contains a response splitting vulnerability in wasi-http p3 that allows guests to set unvalidated content-length headers. Malicious wasip3 guests can splice an existing body into a new response with an incorrect content-length to perform response splitting or injection attacks.
HTTP Request/Response Smuggling
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
VulnCheckCNA
5.3 MEDIUM
NETWORK
LOW
NONE
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Base Score
CVSS 3.x
EPSS Score
Percentile: Unknown
Early Detection
Affected products identified ahead of NVD analysis through intelligence sources (CNA/ADP records, vendor advisories, Enginsight analysis).
VendorProductVersionSource
bytecodealliancewasmtime
46.0.0 ≤
𝑥
< 48.0.7
CNA
bytecodealliancewasmtime
49.0.0 ≤
𝑥
< 49.0.4
CNA
Common Weakness Enumeration
References
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-9prg-84vf-g5fc
https://www.vulncheck.com/advisories/wasmtime-46.0.0-before-48.0.7-and-49.0.0-before-49.0.4-http-response-splitting-via-wasi-http