CVE-2026-121439 json
Wasmtime 46.0.0 before 48.0.7 and 49.0.0 before 49.0.4 HTTP Response Splitting via wasi-http
published 21d ago modified 11h ago also EUVD-2026-115861 , GHSA-9prg-84vf-g5fc , RUSTSEC-2026-0375
- cvss
- 5.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 9%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- crates.io wasmtime-wasi-http 48.0.7, 49.0.4
- bytecodealliance wasmtime 48.0.7, 49.0.4
- github.com/bytecodealliance/wasmtime#14822 pull request
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red hat product security vex CVE-2026-121439 updated cvss 5.3
wasmtime: wasmtime: Response splitting via unvalidated Content-Length headers in wasi-http
-
Red Hat Connectivity Link 1 rhcl-1/wasm-shim-rhel9 Red Hat Enterprise Linux 10 tree-sitter 0.23.0-3.el10, virt-firmware-rs 26.4-1.el10affected: no fix available “Fix deferred”
Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 11h ago
Exploit prediction
0.19% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-09).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N |
| CNA | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |
| CNA | 4.0 | 6.9 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| OSV | 3.1 | 5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| crates.io | wasmtime-wasi-http | >=46.0.0, <48.0.7 >=49.0.0, <49.0.4 |
48.0.7 49.0.4 |
Affected products
- bytecodealliance wasmtime
Classification
- Weakness
-
- CWE-444 Inconsistent Interpretation of HTTP Requests
References
-
github.com
/bytecodealliance/wasmtime/pull/14822
web
-
github.com
/bytecodealliance/wasmtime/security/advisories/GHSA-9prg-84vf-g5fc
vendor-advisory
-
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
third-party-advisory
-
crates.io
/crates/wasmtime-wasi-http
package
-
rustsec.org
/advisories/RUSTSEC-2026-0375.html
advisory
Sources
- CVE List CVE-2026-121439
- NVD CVE-2026-121439
- OSV RUSTSEC-2026-0375
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