CVE-2026-115893: Wasmtime: Cranelift backend on aarch64 can jump to incorrect target on large Wasm `br_table` instruction

Severity: critical (CVSS 9.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-23 · updated 2026-10-29
Weakness: CWE-691

Description

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.

Affected products

bytecodealliance wasmtime: before 36.0.19; from 37.0.0, < 48.0.7; from 49.0.0, < 49.0.4

In the news

Two Critical Wasmtime Flaws Could Let Malicious WebAssembly Modules Escape Sandboxes

References

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