Wasmtime: Preemption and traps during bulk operations enable breaking internal VM state — GHSA-2HW9-MC66-JC2Q

Summary

### Impact Wasmtime's implementation of bulk-data-transfer WebAssembly instructions, such as `memory.copy`, contains a vulnerability when a preemption via epochs or fuel is combined with altering the store's state or cancelling a computation. To prevent these operations from taking too long Wasmtime injects fuel/epoch checks during these operations, but this enables embedders, and possible WebAssembly, to witness…

Timeline

Published by source

2026-10-02

Risk context

• Reported severity or threat level: low.
• Reported CVSS score: 2 out of 10.
• Review exposure for the affected product or family: rust: wasmtime.

Product

rust: wasmtime

What to do

General, cautious steps (verify details in the official source):

• Review exposure and plan remediation based on risk and environment.
• Identify affected product versions in your inventory and verify whether you are impacted.
• Apply vendor patches/updates or recommended mitigations as soon as available.
• Read the official advisory for exact affected versions and remediation steps.

Official advisory

• Read the official source
• CVE Record
• NVD

Evidence and provenance

Canonical advisory ID

GHSA-2HW9-MC66-JC2Q

Source

GitHub

Vendor

GitHub

Published by source

2026-10-02

Last source activity

2026-10-02

Additional identifiers

CVE-2026-104855

Curated by

hlukh.ch

Related advisories and connections

These advisories are connected by shared CVE, product, vendor, source, or time signals.