CVE-2026-121439
Published:November 03, 2026
Updated:November 04, 2026
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.
Affected Packages
https://github.com/bytecodealliance/wasmtime.git (GITHUB):
Affected version(s) =v50.0.0-rc.1 <v50.0.0Fix Suggestion:
Update to version v50.0.0https://github.com/bytecodealliance/wasmtime.git (GITHUB):
Affected version(s) >=v46.0.0 <v48.0.7 || >=v47.0.0 <v48.0.7 || >=v48.0.0 <v48.0.7Fix Suggestion:
Update to version v48.0.7https://github.com/bytecodealliance/wasmtime.git (GITHUB):
Affected version(s) >=v49.0.0-rc.1 <v49.0.4Fix Suggestion:
Update to version v49.0.4wasmtime-wasi-http (RUST):
Affected version(s) =50.0.0-rc.1 <50.0.0Fix Suggestion:
Update to version 50.0.0wasmtime-wasi-http (RUST):
Affected version(s) >=46.0.0 <48.0.7 || >=47.0.0 <48.0.7 || >=48.0.0 <48.0.7Fix Suggestion:
Update to version 48.0.7wasmtime-wasi-http (RUST):
Affected version(s) >=49.0.0-rc.1 <49.0.4Fix Suggestion:
Update to version 49.0.4Related Resources (7)
Do you need more information?
Contact UsCVSS v4
Base Score:
6.9
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Inconsistent Interpretation of HTTP Requests
EPSS
Base Score:
0.19