CVE-2026-126409
Deferred Deferred - Pending Action

Type Confusion in Wasmtime Due to Engine Boundary Violation

Publication date: 2026-11-13

Last updated on: 2026-11-13

Assigner: VulnCheck

Description
Wasmtime 47.0.0 before 48.0.8, 49.0.0 before 49.0.5, and 50.0.0 before 50.0.1 contains a cross-engine type confusion vulnerability because StructType::with_finality_and_supertype does not validate that the supplied supertype belongs to the same Engine. Embedders using multiple engines that create a GC struct type with another engine's supertype can trigger runtime panics or GC heap corruption, causing denial of service; guest WebAssembly cannot trigger it.

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Meta Information

Published
2026-11-13
Last Modified
2026-11-13
Generated
2026-11-13
AI Q&A
2026-11-13
EPSS Evaluated
N/A
NVD
CVE-2026-126409
EUVD
EUVD-2026-125034

Affected Vendors & Products

Showing 6 associated CPEs
Vendor Product Version / Range
wasmtime wasmtime to 48.0.8 (exc)
wasmtime wasmtime to 49.0.5 (exc)
wasmtime wasmtime to 50.0.1 (exc)
bytecodealliance wasmtime From 47.0.0 (inc) to 48.0.7 (inc)
bytecodealliance wasmtime From 49.0.0 (inc) to 49.0.4 (inc)
bytecodealliance wasmtime 50.0.0

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-843 The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.

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Executive Summary

This vulnerability is a cross-engine type confusion in Wasmtime versions 47.0.0 to 48.0.7, 49.0.0 to 49.0.4, and 50.0.0. It occurs when the StructType::with_finality_and_supertype function does not check if the supertype belongs to the same engine. This allows embedders using multiple engines to create a GC struct type with a supertype from a different engine, potentially causing runtime panics or GC heap corruption.

Impact Analysis

The impact includes runtime crashes, garbage collection heap corruption, or denial-of-service conditions. However, guest WebAssembly cannot trigger this vulnerability. Exploitation requires embedders to use at least two engines and specific conditions, making it difficult for typical users to be affected.

Mitigation Strategies

Update Wasmtime to versions 48.0.8 or later, 49.0.5 or later, or 50.0.1 or later to address the cross-engine type confusion vulnerability.

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