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vm2: util.getCallSites() bypasses GHSA-v27g-jcqj-v8rw host-frame redaction, leaks host call stack

Moderate severity GitHub Reviewed Published Aug 27, 2026 in patriksimek/vm2 • Updated Oct 5, 2026

Package

npm vm2 (npm)

Affected versions

<= 3.11.7

Patched versions

3.11.8

Description

Summary

NodeVM exposes the host util module to the sandbox through an unfiltered shallow copy (Object.assign({}, util)). On Node.js >= 22.9 this hands sandboxed code util.getCallSites(), a programmatic stack-introspection API that returns the host process's full call stack — absolute file paths, function names, and line numbers — including vm2 bridge internals and the embedding application's entrypoint. This bypasses the host-frame redaction established in GHSA-v27g-jcqj-v8rw, which only covers the Error.prepareStackTrace channel.

Details

util.getCallSites() produces its data host-side and never passes through that formatter, so frames such as lib/bridge.js @apply (the bridge apply trap), lib/nodevm.js @run, the embedder's own entry file, and node:internal/* frames reach the sandbox verbatim as data properties (scriptName, functionName, lineNumber, columnNumber, scriptId). A repository-wide grep (source, docs/ATTACKS.md, CHANGELOG, tests) shows no occurrence of getCallSites; the member was never considered.

PoC

Prerequisites: Node.js >= 22.9 (verified on v22.23.1); run npm ci --no-audit --no-fund at the repository root.

One-line reproducer (prints /workspace/repo/lib/bridge.js, i.e. a vm2-internal host path):

node -e "const {NodeVM}=require('/workspace/repo'); console.log(new NodeVM({require:{builtin:['util']}}).run(\"module.exports = require('util').getCallSites(4)[0].scriptName\"))"

Observed frames inside the sandbox, with both require: { builtin: ['util'] } and require: { builtin: ['*'] }:

/workspace/repo/lib/bridge.js @apply:1664
vm.js @:5
/workspace/repo/lib/bridge.js @apply:1664
/workspace/repo/lib/nodevm.js @run:563
/workspace/out/<embedder entrypoint>.js @main:29
node:internal/modules/cjs/loader @:1781
node:internal/modules/cjs/loader @:1913
... (8 node:internal/* frames in total)

Impact

Information disclosure. Any NodeVM configuration that allows the util (or sys) builtin — including the wildcard builtin: ['*'], both typical configurations from the README — lets untrusted sandboxed code programmatically read the host call stack: the vm2 installation path, the embedding application's file layout and entrypoint, and internal function names and line numbers. This is the same information category redacted by GHSA-v27g-jcqj-v8rw (Defense Invariant #5 in docs/ATTACKS.md) and breaks defense-in-depth assumptions of embedders that rely on host frames being invisible to the sandbox. The API returns only strings/numbers (no host object references); no escalation to code execution was identified.

Suggested fix: filter members in defaultBuiltinLoaderUtil (allowlist, or at minimum drop getCallSites), apply the same treatment to the generic loader path used by sys, and extend the GHSA-v27g regression tests to cover programmatic stack-introspection APIs.

References

@patriksimek patriksimek published to patriksimek/vm2 Aug 27, 2026
Published to the GitHub Advisory Database Oct 5, 2026
Reviewed Oct 5, 2026
Last updated Oct 5, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality Low
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(29th percentile)

Weaknesses

Exposure of Sensitive Information to an Unauthorized Actor

The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Learn more on MITRE.

Protection Mechanism Failure

The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product. Learn more on MITRE.

CVE ID

CVE-2026-92933

GHSA ID

GHSA-r273-hxvj-fxhp

Source code

Credits

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