CVE-2026-121441 json
Wasmtime before 36.0.19, 37.0.0 before 48.0.7, and 49.0.0 before 49.0.4 wasi-http Request Smuggling
published 25d ago modified 10d ago also EUVD-2026-115863 , GHSA-r8xh-cgf7-392j , RUSTSEC-2026-0376
- cvss
- 3.7
- 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 13%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- crates.io wasmtime-wasi-http 36.0.19, 48.0.7, 49.0.4
- bytecodealliance wasmtime 36.0.19, 48.0.7, 49.0.4
- github.com/bytecodealliance/wasmtime#14824 pull request
Is CVE-2026-121441 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.
Check with FencerVendor advisories
What the vendors themselves say about their products: affected, fixed or not affected, and what to do.
red hat product security vex CVE-2026-121441 updated cvss 3.7
wasmtime: wasmtime: HTTP request smuggling via multiple conflicting Content-Length headers
-
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
- no
- Technical impact
- partial
- Assessed
- 10d ago
Exploit prediction
0.22% chance of exploitation in the next 30 days, higher than 13% of all scored CVEs (FIRST EPSS, 2026-11-13).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 6.3 | 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 |
| CNA | 3.1 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
| CNA | 4.0 | 6.3 | 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/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 | 3.7 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| crates.io | wasmtime-wasi-http | >=0.0.0-0, <36.0.19 >=37.0.0, <48.0.7 >=49.0.0, <49.0.4 |
36.0.19 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/14824
web
-
github.com
/bytecodealliance/wasmtime/security/advisories/GHSA-r8xh-cgf7-392j
vendor-advisory, advisory
-
vulncheck.com
/advisories/wasmtime-before-36.0.19-37.0.0-before-48.0.7-and-49.0.0-before-49.0.4-wasi-http-request-smuggling
third-party-advisory
-
crates.io
/crates/wasmtime-wasi-http
package
-
rustsec.org
/advisories/RUSTSEC-2026-0376.html
advisory
Sources
- CVE List CVE-2026-121441
- NVD CVE-2026-121441
- OSV RUSTSEC-2026-0376
- Maintainer advisory GHSA-r8xh-cgf7-392j
Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
The maintainers of bytecodealliance/wasmtime published their own advisory on GitHub. Reviewed sources take precedence over it.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.