Out-of-bounds Read Affecting rust-wasmtime package, versions *


Severity

Recommended
0.0
critical
0
10

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Threat Intelligence

EPSS
0.28% (20th percentile)

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  • Snyk IDSNYK-DEBIAN13-RUSTWASMTIME-15996457
  • published12 Apr 2026
  • disclosed9 Apr 2026

Introduced: 9 Apr 2026

CVE-2026-34987  (opens in a new tab)
CWE-125  (opens in a new tab)
CWE-787  (opens in a new tab)

How to fix?

There is no fixed version for Debian:13 rust-wasmtime.

NVD Description

Note: Versions mentioned in the description apply only to the upstream rust-wasmtime package and not the rust-wasmtime package as distributed by Debian. See How to fix? for Debian:13 relevant fixed versions and status.

Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has an observed-working proof of concept, while the x86-64 case is theoretical and may not be reachable in practice. This Winch compiler bug can allow the Wasm guest to access memory before or after the linear-memory region, independently of whether pre- or post-guard regions are configured. The accessible range in the initial bug proof-of-concept is up to 32KiB before the start of memory, or ~4GiB after the start of memory, independently of the size of pre- or post-guard regions or the use of explicit or guard-region-based bounds checking. However, the underlying bug assumes a 32-bit memory offset stored in a 64-bit register has its upper bits cleared when it may not, and so closely related variants of the initial proof-of-concept may be able to access truly arbitrary memory in-process. This could result in a host process segmentation fault (DoS), an arbitrary data leak from the host process, or with a write, potentially an arbitrary RCE. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.

CVSS Base Scores

version 3.1