CVE-2026-121441 PUBLISHED

Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 wasi-http Request Smuggling

Assigner: VulnCheck
Reserved: 03.11.2026 Published: 03.11.2026 Updated: 03.11.2026

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.

CVSS Vector: 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
CVSS Score: 6.3

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	None	Confidentiality	None
Attack Complexity	High	Integrity	Low	Integrity	None
Attack Requirements	Present	Availability	None	Availability	None
Privileges Required	None
User Interaction	None

CVSS 4.0

CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
CVSS Score: 3.7

Attack Vector	Network	Scope	Unchanged
Attack Complexity	High	Confidentiality Impact	None
Privileges Required	None	Integrity Impact	Low
User Interaction	None	Availability Impact	None

CVSS 3.1

Product Status

Vendor	bytecodealliance
Product	wasmtime
Versions	Default: unaffected affected from 0 to 36.0.19 (excl.) Version 36.0.19 is unaffected affected from 37.0.0 to 48.0.7 (excl.) Version 48.0.7 is unaffected affected from 49.0.0 to 49.0.4 (excl.) Version 49.0.4 is unaffected

References

Problem Types

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling') CWE