# CVE-2026-115893: Wasmtime Cranelift aarch64 br_table sandbox escape

Source: https://junglewise.ai/threats/cve-2026-115893-wasmtime-is-a-runtime-for-webassembly-prior-to-36-0-19-48-0-7  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-23. Updated: 2026-10-23  
License: CC BY 4.0 with a link back

CVE-2026-115893 · Severity: critical · CVSS 9.9 · Published 2026-10-23

Wasmtime is a runtime that executes WebAssembly code in a sandboxed environment. A flaw in the Cranelift compiler on aarch64 processors allows a malicious WebAssembly module with a large branch table to break out of the sandbox and execute arbitrary code by jumping to attacker-controlled memory addresses. This enables complete compromise of systems running untrusted WebAssembly modules.

Technologies: [Bytecode Alliance Wasmtime](https://junglewise.ai/threats/technologies/bytecode-alliance-wasmtime), [wasmtime (crates.io)](https://junglewise.ai/threats/technologies/wasmtime). Vendors: [Bytecode Alliance](https://junglewise.ai/threats/vendors/bytecode-alliance), [crates.io](https://junglewise.ai/threats/vendors/crates-io).

## Quick answers

**Is CVE-2026-115893 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-115893 being exploited in the wild.

**How severe is CVE-2026-115893?** Critical severity, with a CVSS score of 9.9, published 23 October 2026.

**Which products and versions are affected?** Bytecode Alliance Wasmtime before 36.0.19, 48.0.7, and 49.0.4; wasmtime (crates.io) < 36.0.19, SEMVER:introduced=0,fixed=36.0.19.

**Is there a fix for CVE-2026-115893?** Yes. wasmtime (crates.io): upgrade to 36.0.19 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-115893 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-115893?** Check whether you run Bytecode Alliance Wasmtime or wasmtime (crates.io) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- wasmtime (crates.io): upgrade to 36.0.19 or later

  ```sh
  cargo update -p wasmtime
  ```


## Technical details

The Cranelift compiler backend on aarch64 incorrectly compiles WebAssembly br_table instructions with over approximately 256,000 targets, resulting in an out-of-bounds branch offset that wraps and jumps to an attacker-specified memory location. The vulnerability stems from a conditional branch with a ±1 MiB range being used for the default case when the table offset exceeds available space. An attacker with control over a Wasm module can trigger this to escape the sandbox.

## Affected products

- Bytecode Alliance Wasmtime before 36.0.19, 48.0.7, and 49.0.4

## Identifiers

- CVE-2026-115893
- GHSA-mghf-wjfp-p5xm
- RUSTSEC-2026-0379

## Timeline

- 2026-10-23: disclosed
- 2026-10-19: patched

## References

- [https://github.com/bytecodealliance/wasmtime/commit/222ff3a65dab9aa7011f8c246937751a0bac5abd](https://github.com/bytecodealliance/wasmtime/commit/222ff3a65dab9aa7011f8c246937751a0bac5abd)
- [https://github.com/bytecodealliance/wasmtime/commit/994549891c8a706cb4f2809f9d17b9f67b31e618](https://github.com/bytecodealliance/wasmtime/commit/994549891c8a706cb4f2809f9d17b9f67b31e618)

## Related threats

- [Wasmtime wasi-http response splitting via unvalidated headers](https://junglewise.ai/threats/cve-2026-121439-wasmtime-46-0-0-before-48-0-7-and-49-0-0-before-49-0-4-contains)
- [Wasmtime denial of service in component model stream operations](https://junglewise.ai/threats/cve-2026-119143-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime host panic in call_async Future drop](https://junglewise.ai/threats/cve-2026-119142-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime denial of service in realloc handling](https://junglewise.ai/threats/cve-2026-119141-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)
- [Wasmtime denial of service via thread.yield in component start](https://junglewise.ai/threats/cve-2026-119140-wasmtime-46-0-0-before-48-0-6-and-49-0-0-before-49-0-3-contains)