Two critical Wasmtime flaws (CVSS 9.9) let malicious Wasm modules escape sandboxes
jedisct1 · x · 2026-10-26
Two critical flaws in Wasmtime, the WebAssembly runtime, could let malicious Wasm modules escape their sandbox. The Bytecode Alliance rated both 9.9/10 on CVSS.
- CVE-2026-115889 affects all architectures; CVE-2026-115893 affects only ARM64 (aarch64)
- Both bugs are in Cranelift, Wasmtime's default compiler from Wasm to machine code
- Fixed versions shipped October 19–20; maintainers report no attacks so far, and neither flaw was in CISA's Known Exploited Vulnerabilities catalog as of October 26
- Exploitation requires the target to compile an attacker-controlled module, so the highest risk is for services compiling third-party modules — e.g. Fastly's Compute platform runs customer code on Wasmtime
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