CVE-2026-26956Public exploitNetwork attack vector

Host code execution via unsanitized WASM-caught errors

Published May 4, 2026 · Updated May 4, 2026

Sandbox escape in Patrik Simek vm2 3.10.4 allows attackers to execute arbitrary host code through untrusted input to VM.run(). A WebAssembly try_table handler catches a host-realm TypeError below vm2's JavaScript instrumentation and returns it unsanitized as an externref. Exploitation requires Node.js 25 with WebAssembly exception handling and JSTag support, after which the error's constructor chain exposes the host process.

CVSS severity9.8
Critical
EPSS probability0.92%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Sandbox escape in Patrik Simek vm2 3.10.4 allows attackers to execute arbitrary host code through untrusted input to VM.run(). A WebAssembly try_table handler catches a host-realm TypeError below vm2's JavaScript instrumentation and returns it unsanitized as an externref. Exploitation requires Node.js 25 with WebAssembly exception handling and JSTag support, after which the error's constructor chain exposes the host process.

The record

CVE
CVE-2026-26956
Published
May 4, 2026
Updated
May 4, 2026
Vendor
Patrik Simek
Product
vm2
Classifications
CWE-653, CWE-693, T1059.007
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 4, 2026CVE publishedPublication date reported by the CVE source.
  2. May 4, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion== 3.10.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Patrik Simek · vm2version== 3.10.4

Published CVSS scores

9.8GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8redhat-SADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-653Improper Isolation or Compartmentalization
CWE-693Protection Mechanism Failure
T1059.007JavaScript/JScript

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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