WebAssembly Runtime Vulnerability in Wasmtime by Bytecode Alliance
CVE-2026-34945

2.3LOW

Key Information:

Vendor

Bytecodealliance

Status
Wasmtime
Vendor
CVE Published:
9 April 2026

What is CVE-2026-34945?

The Wasmtime runtime for WebAssembly has a vulnerability in its Winch compiler affecting versions from 25.0.0 up to, but not including, 36.0.7, 42.0.1, and 43.0.1. A misimplementation of the table.size instruction for a 64-bit table has been identified, which could result in sensitive data from the host's stack being exposed to WebAssembly guests. This significant flaw arises from mishandling the return value type for table size, treating it as a 32-bit integer instead of reflecting the actual size according to the table's index type. The implications of this bug could potentially lead to unauthorized access to sensitive information not meant to be disclosed. Users are advised to update to patched versions to mitigate this risk.

Affected Version(s)

wasmtime >= 25.0.0, < 36.0.7 < 25.0.0, 36.0.7

wasmtime >= 37.0.0, < 42.0.2 < 37.0.0, 42.0.2

wasmtime >= 43.0.0, < 44.0.1 < 43.0.0, 44.0.1

References

https://github.com/bytecodealliance/wasmtime/security/adv...
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CVSS V4

Score:
2.3
Severity:
LOW
Confidentiality:
Low
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
Physical
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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