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Vulnerability · Published Oct 2, 2026 · Assigned by GitHub_M

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

Low 2.0

In plain English

A low-severity race condition in wasmtime from bytecodealliance. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 20% of all known vulnerabilities).

Severity (CVSS 4.0)2.0Low
Exploit odds (30 days)0.3%top 79.9% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Ubuntu:24.04:LTSrust-wasmtimeno fix listedUBUNTU-CVE-2026-104855
Ubuntu:26.04:LTSrust-wasmtimeno fix listedUBUNTU-CVE-2026-104855
Ubuntu:26.10rust-wasmtimeno fix listedUBUNTU-CVE-2026-104855

Affected products (as reported)

VendorProductVersions
bytecodealliance wasmtime >= 46.0.0, < 46.0.2>= 47.0.0, < 47.0.3

Weakness: CWE-362 · 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

References