If you use Wasmtime to run untrusted WebAssembly (plugins, serverless functions, or tool code from agents), a malicious module can break out of the sandbox with default settings. Both bugs are rated CVSS 9.9:

• CVE-2026-115889: Cranelift packed its internal value indices too tightly. A huge or specially built Wasm function can overflow them silently in release builds, causing miscompilation and a sandbox escape on any platform. Wasmtime 43 and later are not affected. Older lines are fixed in 36.0.19.
• CVE-2026-115893: on aarch64, a br_table with more than about 256k targets can compile to a wrong branch target, letting the module jump to code at an offset it controls. This affects every Wasmtime version with aarch64 support since 2020. Fixed in 36.0.19, 48.0.7 and 49.0.4 (50.0.0 is also out).

Upgrade, and check for embedded copies: many Rust projects vendor Wasmtime, so run cargo tree -i wasmtime or check your SBOM. The project has not reported any exploitation.