Two critical Wasmtime flaws let malicious WebAssembly modules escape the sandbox
CVE-2026-115889 affects every architecture and CVE-2026-115893 only ARM64; fixes landed October 19–20 with no attacks reported.
64
CVE-2026-115893
Wasmtime Cranelift sandbox escape on aarch64
- CVSS 3.1
- 9.9 critical
- EPSS
- <1%p63
- Published
- ·
- Modified
AI analysisSummaries by Vani AI
In Wasmtime before 36.0.19, 48.0.7, and 49.0.4, the Cranelift backend on aarch64 can miscompile a Wasm br_table with more than about 256,000 targets, so a conditional branch uses the wrong target. A user who can supply a Wasm module can make that branch jump to other code at a chosen offset and escape the sandbox. Only aarch64 engines using the default Cranelift backend are affected.
What to do: Upgrade Wasmtime to 36.0.19, 48.0.7, or 49.0.4.
| Product | Affected | Fixed in |
|---|---|---|
| Wasmtime | Prior to 36.0.19, 48.0.7, and 49.0.4 | 36.0.19, 48.0.7, and 49.0.4 |
Estimated exposure
No basis for an estimate.
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description · NVD
Wasmtime is a runtime for WebAssembly. Prior to 36.0.19, 48.0.7, and 49.0.4, the Cranelift compiler backend on aarch64 can compile a Wasm br_table instruction with more than approximately 256,000 targets so that it has an incorrect conditional branch target. The branch can then jump to arbitrary other code at a user-controlled offset, allowing a user-controlled Wasm module to escape the sandbox on aarch64 engines using the default Cranelift backend. This issue is fixed in versions 36.0.19, 48.0.7, and 49.0.4.
- Ecosystems
- rust
- Weakness
- CWE-691
- Vector
- CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
- GHSA
- GHSA-mghf-wjfp-p5xm (critical)