Vulnerability-Lookup

CVE-2026-47683 (GCVE-0-2026-47683)

Vulnerability from cvelistv5 – Published: 2026-08-17 20:55 – Updated: 2026-08-18 15:38

Title

vm2: bufferAllocLimit cap bypassed by Buffer.concat and Buffer.from arrayLike

Summary

vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.6, the bufferAllocLimit enforcement in lib/setup-sandbox.js does not cover Buffer.concat(list, totalLength) or Buffer.from(arrayLike) with an attacker-controlled length, allowing sandbox code to perform large synchronous host external-memory allocations that bypass the configured cap and can exhaust the host process. This issue is fixed in version 3.11.6.

Severity

8.7 (High)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

SSVC

Exploitation: poc Automatable: yes Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-18 15:38 UTC

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/patriksimek/vm2/security/advis…	x_refsource_CONFIRM
https://github.com/patriksimek/vm2/commit/3ffb315…	x_refsource_MISC
https://github.com/patriksimek/vm2/releases/tag/3.11.6	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
patriksimek	vm2	Affected: < 3.11.6	guessed

Show details on NVD website

JSON

To clipboard

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}

FKIE_CVE-2026-47683

Vulnerability from fkie_nvd - Published: 2026-08-17 21:16 - Updated: 2026-09-09 21:11

Severity

8.7 (High) - CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/patriksimek/vm2/commit/3ffb315512e634cf85c447375e85d6c83d00a4bd
	security-advisories@github.com	https://github.com/patriksimek/vm2/releases/tag/3.11.6
	security-advisories@github.com	https://github.com/patriksimek/vm2/security/advisories/GHSA-gmc2-2x9w-cgh9
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/patriksimek/vm2/security/advisories/GHSA-gmc2-2x9w-cgh9

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "vm2",
          "vendor": "patriksimek",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 3.11.6"
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    }
  ],
  "id": "CVE-2026-47683",
  "lastModified": "2026-09-09T21:11:46.833",
  "metrics": {
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          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 8.7,
          "baseSeverity": "HIGH",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
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          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
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GHSA-GMC2-2X9W-CGH9

Vulnerability from github – Published: 2026-08-17 17:32 – Updated: 2026-08-17 17:32

Summary

vm2's bufferAllocLimit cap bypassed by Buffer.concat and Buffer.from arrayLike

Details

Summary

vm2 bufferAllocLimit cap bypassed by Buffer.concat and Buffer.from arrayLike

The bufferAllocLimit option introduced in 3.11.0 (GHSA-6785-pvv7-mvg7) caps host-side Buffer allocations driven by sandbox code, the way embedders opt into timeout. The cap wraps Buffer.alloc, Buffer.allocUnsafe, Buffer.allocUnsafeSlow, and the deprecated Buffer(N) / new Buffer(N) forms. Two other API paths reach the same host C++ allocator with an attacker-controlled size and are not capped: Buffer.concat(list, totalLength) and Buffer.from(arrayLike) with a fake length. Sandbox code can use either to allocate an arbitrary number of host external bytes in a single call, defeating the explicit DoS mitigation the embedder configured.

Details

lib/setup-sandbox.js installs checkBufferAllocLimit at every wrapped entry to host Buffer allocation:

alloc() at lib/setup-sandbox.js:474 and the connect(alloc, host.Buffer.alloc) at line 480.
allocUnsafe() at line 488 and connect(allocUnsafe, host.Buffer.allocUnsafe) at line 496.
allocUnsafeSlow() at line 504 and connect(allocUnsafeSlow, host.Buffer.allocUnsafeSlow) at line 510.
BufferHandler.apply at line 424 and BufferHandler.construct at line 433 for the deprecated Buffer(N) / new Buffer(N) numeric-first-arg paths.

Buffer.concat is not wrapped. The sandbox-visible Buffer.concat is therefore the bridge proxy of the host Buffer.concat, which calls into Node's Buffer.allocUnsafe(totalLength) internally without going through the sandbox-side allocUnsafe wrapper. Same for Buffer.from when the argument is array-like ({length: N}): Node's fromArrayLike allocates a buffer of size N before the iteration that fills it. Neither of those allocator paths consult localBufferAllocLimit.

The mitigation rationale documented in docs/ATTACKS.md Category 23 explicitly enumerates the surfaces that were considered and either capped (Buffer.alloc family) or punted to follow-up (new Uint8Array(N), new ArrayBuffer(N), String.prototype.repeat). Buffer.concat(list, totalLength) is not listed in either group, and Buffer.from(arrayLike) is mentioned only as "bounded by source array size which had to be allocated through some other path first" -- which is not true for the {length: N} form, because no array of length N actually exists.

A single call from sandbox to Buffer.concat([Buffer.from('a')], 50 * 1024 * 1024) allocates 50 MiB of host external memory. The allocation itself is a single synchronous host C++ call that timeout cannot interrupt, exactly like the original advisory. The zero-fill that follows is interruptible, but the memory is already committed by the time the interrupt could fire, so the embedder's container memory budget is the only ceiling. The same pattern in a loop, or with a larger totalLength, drives RSS up by hundreds of megabytes per call.

The fix uses the existing checkBufferAllocLimit(size) helper and a sandbox-side wrapper installed via connect(...) -- one for Buffer.concat that sums the totalLength (or falls back to summing list lengths) and one for Buffer.from that recognises the array-like-with-numeric-length branch.

PoC

'use strict';
const { VM, NodeVM } = require('vm2');

function ext() { return Math.round(process.memoryUsage().external / 1024 / 1024); }
function tryBypass(label, code) {
    const ext0 = ext();
    let buf;
    try { buf = code(); }
    catch (e) {
        console.log(`[${label}] CAPPED -- ${String(e).split('\n')[0]}`);
        return;
    }
    console.log(`[${label}] BYPASSED -- got ${buf && buf.length} bytes (external +${ext() - ext0} MB)`);
}

console.log('Cap is configured at 1024 bytes.\n');

const vm1 = new VM({ bufferAllocLimit: 1024 });
tryBypass('VM Buffer.alloc(50MB)        ',
    () => vm1.run('Buffer.alloc(50 * 1024 * 1024)'));

const vm2 = new VM({ bufferAllocLimit: 1024 });
tryBypass('VM Buffer.concat 50MB        ',
    () => vm2.run('Buffer.concat([Buffer.from("a")], 50 * 1024 * 1024)'));

const vm3 = new NodeVM({ bufferAllocLimit: 1024 });
tryBypass('NodeVM Buffer.concat 50MB    ',
    () => vm3.run('module.exports = Buffer.concat([Buffer.from("a")], 50 * 1024 * 1024);'));

const vm4 = new VM({ bufferAllocLimit: 1024 });
tryBypass('VM Buffer.from({length: 8MB})',
    () => vm4.run('Buffer.from({length: 8 * 1024 * 1024})'));

Run with node poc.js against vm2@3.11.3:

Cap is configured at 1024 bytes.

[VM Buffer.alloc(50MB)        ] CAPPED -- RangeError: Buffer allocation size 52428800 exceeds bufferAllocLimit 1024
[VM Buffer.concat 50MB        ] BYPASSED -- got 52428800 bytes (external +50 MB)
[NodeVM Buffer.concat 50MB    ] BYPASSED -- got 52428800 bytes (external +50 MB)
[VM Buffer.from({length: 8MB})] BYPASSED -- got 8388608 bytes (external +8 MB)

Process RSS climbs by the same amount each call, confirming a real host C++ allocation rather than a sandbox-realm-only effect.

Impact

This is the same DoS class GHSA-6785-pvv7-mvg7 was filed for: untrusted sandbox code amplifying a small payload into a large synchronous host external-memory allocation that V8's timeout cannot preempt. In the environments the advisory cites -- Docker memory limits, Kubernetes pods, AWS Lambda -- a single 200-byte sandbox payload can drive a multi-hundred-megabyte RSS jump and OOM the host process.

The Category 23 fix was specifically scoped to "cap host Buffer external allocation" and embedders are documented to opt into bufferAllocLimit as their layered defense against this class. The two paths above are uncapped, so an embedder that has configured bufferAllocLimit: 32 * 1024 * 1024 (the value recommended in the README's Hardening recommendations) is still vulnerable to the exact attack the option was designed to prevent. The mitigation invariant -- "every Buffer external allocation driven by sandbox code is capped by bufferAllocLimit" -- does not hold.

No sandbox escape; pure DoS.

Severity

8.7 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.11.5"
      },
      "package": {
        "ecosystem": "npm",
        "name": "vm2"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.11.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-47683"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-17T17:32:10Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nvm2 bufferAllocLimit cap bypassed by Buffer.concat and Buffer.from arrayLike\n\nThe `bufferAllocLimit` option introduced in 3.11.0 (GHSA-6785-pvv7-mvg7) caps host-side Buffer allocations driven by sandbox code, the way embedders opt into `timeout`. The cap wraps `Buffer.alloc`, `Buffer.allocUnsafe`, `Buffer.allocUnsafeSlow`, and the deprecated `Buffer(N)` / `new Buffer(N)` forms. Two other API paths reach the same host C++ allocator with an attacker-controlled size and are not capped: `Buffer.concat(list, totalLength)` and `Buffer.from(arrayLike)` with a fake `length`. Sandbox code can use either to allocate an arbitrary number of host external bytes in a single call, defeating the explicit DoS mitigation the embedder configured.\n\n## Details\n\n`lib/setup-sandbox.js` installs `checkBufferAllocLimit` at every wrapped entry to host Buffer allocation:\n\n- `alloc()` at `lib/setup-sandbox.js:474` and the `connect(alloc, host.Buffer.alloc)` at line 480.\n- `allocUnsafe()` at line 488 and `connect(allocUnsafe, host.Buffer.allocUnsafe)` at line 496.\n- `allocUnsafeSlow()` at line 504 and `connect(allocUnsafeSlow, host.Buffer.allocUnsafeSlow)` at line 510.\n- `BufferHandler.apply` at line 424 and `BufferHandler.construct` at line 433 for the deprecated `Buffer(N)` / `new Buffer(N)` numeric-first-arg paths.\n\n`Buffer.concat` is not wrapped. The sandbox-visible `Buffer.concat` is therefore the bridge proxy of the host `Buffer.concat`, which calls into Node\u0027s `Buffer.allocUnsafe(totalLength)` internally without going through the sandbox-side `allocUnsafe` wrapper. Same for `Buffer.from` when the argument is array-like (`{length: N}`): Node\u0027s `fromArrayLike` allocates a buffer of size `N` before the iteration that fills it. Neither of those allocator paths consult `localBufferAllocLimit`.\n\nThe mitigation rationale documented in `docs/ATTACKS.md` Category 23 explicitly enumerates the surfaces that were considered and either capped (Buffer.alloc family) or punted to follow-up (`new Uint8Array(N)`, `new ArrayBuffer(N)`, `String.prototype.repeat`). `Buffer.concat(list, totalLength)` is not listed in either group, and `Buffer.from(arrayLike)` is mentioned only as \"bounded by source array size which had to be allocated through some other path first\" -- which is not true for the `{length: N}` form, because no array of length `N` actually exists.\n\nA single call from sandbox to `Buffer.concat([Buffer.from(\u0027a\u0027)], 50 * 1024 * 1024)` allocates 50 MiB of host external memory. The allocation itself is a single synchronous host C++ call that `timeout` cannot interrupt, exactly like the original advisory. The zero-fill that follows is interruptible, but the memory is already committed by the time the interrupt could fire, so the embedder\u0027s container memory budget is the only ceiling. The same pattern in a loop, or with a larger `totalLength`, drives RSS up by hundreds of megabytes per call.\n\nThe fix uses the existing `checkBufferAllocLimit(size)` helper and a sandbox-side wrapper installed via `connect(...)` -- one for `Buffer.concat` that sums the `totalLength` (or falls back to summing list lengths) and one for `Buffer.from` that recognises the array-like-with-numeric-`length` branch.\n\n## PoC\n\n```javascript\n\u0027use strict\u0027;\nconst { VM, NodeVM } = require(\u0027vm2\u0027);\n\nfunction ext() { return Math.round(process.memoryUsage().external / 1024 / 1024); }\nfunction tryBypass(label, code) {\n    const ext0 = ext();\n    let buf;\n    try { buf = code(); }\n    catch (e) {\n        console.log(`[${label}] CAPPED -- ${String(e).split(\u0027\\n\u0027)[0]}`);\n        return;\n    }\n    console.log(`[${label}] BYPASSED -- got ${buf \u0026\u0026 buf.length} bytes (external +${ext() - ext0} MB)`);\n}\n\nconsole.log(\u0027Cap is configured at 1024 bytes.\\n\u0027);\n\nconst vm1 = new VM({ bufferAllocLimit: 1024 });\ntryBypass(\u0027VM Buffer.alloc(50MB)        \u0027,\n    () =\u003e vm1.run(\u0027Buffer.alloc(50 * 1024 * 1024)\u0027));\n\nconst vm2 = new VM({ bufferAllocLimit: 1024 });\ntryBypass(\u0027VM Buffer.concat 50MB        \u0027,\n    () =\u003e vm2.run(\u0027Buffer.concat([Buffer.from(\"a\")], 50 * 1024 * 1024)\u0027));\n\nconst vm3 = new NodeVM({ bufferAllocLimit: 1024 });\ntryBypass(\u0027NodeVM Buffer.concat 50MB    \u0027,\n    () =\u003e vm3.run(\u0027module.exports = Buffer.concat([Buffer.from(\"a\")], 50 * 1024 * 1024);\u0027));\n\nconst vm4 = new VM({ bufferAllocLimit: 1024 });\ntryBypass(\u0027VM Buffer.from({length: 8MB})\u0027,\n    () =\u003e vm4.run(\u0027Buffer.from({length: 8 * 1024 * 1024})\u0027));\n```\n\nRun with `node poc.js` against `vm2@3.11.3`:\n\n```\nCap is configured at 1024 bytes.\n\n[VM Buffer.alloc(50MB)        ] CAPPED -- RangeError: Buffer allocation size 52428800 exceeds bufferAllocLimit 1024\n[VM Buffer.concat 50MB        ] BYPASSED -- got 52428800 bytes (external +50 MB)\n[NodeVM Buffer.concat 50MB    ] BYPASSED -- got 52428800 bytes (external +50 MB)\n[VM Buffer.from({length: 8MB})] BYPASSED -- got 8388608 bytes (external +8 MB)\n```\n\nProcess RSS climbs by the same amount each call, confirming a real host C++ allocation rather than a sandbox-realm-only effect.\n\n## Impact\n\nThis is the same DoS class GHSA-6785-pvv7-mvg7 was filed for: untrusted sandbox code amplifying a small payload into a large synchronous host external-memory allocation that V8\u0027s `timeout` cannot preempt. In the environments the advisory cites -- Docker memory limits, Kubernetes pods, AWS Lambda -- a single 200-byte sandbox payload can drive a multi-hundred-megabyte RSS jump and OOM the host process.\n\nThe Category 23 fix was specifically scoped to \"cap host Buffer external allocation\" and embedders are documented to opt into `bufferAllocLimit` as their layered defense against this class. The two paths above are uncapped, so an embedder that has configured `bufferAllocLimit: 32 * 1024 * 1024` (the value recommended in the README\u0027s Hardening recommendations) is still vulnerable to the exact attack the option was designed to prevent. The mitigation invariant -- \"every Buffer external allocation driven by sandbox code is capped by `bufferAllocLimit`\" -- does not hold.\n\nNo sandbox escape; pure DoS.",
  "id": "GHSA-gmc2-2x9w-cgh9",
  "modified": "2026-08-17T17:32:10Z",
  "published": "2026-08-17T17:32:10Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/patriksimek/vm2/security/advisories/GHSA-gmc2-2x9w-cgh9"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/patriksimek/vm2"
    },
    {
      "type": "WEB",
      "url": "https://github.com/patriksimek/vm2/releases/tag/3.11.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "vm2\u0027s bufferAllocLimit cap bypassed by Buffer.concat and Buffer.from arrayLike"
}

WID-SEC-W-2026-2865

Vulnerability from csaf_certbund - Published: 2026-08-16 22:00 - Updated: 2026-09-17 22:00

Summary

vm2: Mehrere Schwachstellen

Severity

Kritisch

Scope

5 vulnerabilities in this advisory, including CVE-2026-47683.

CVE-2026-47683

Known affected: 1 product

Open the full advisory

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

CVE-2026-47683 (GCVE-0-2026-47683)

FKIE_CVE-2026-47683

GHSA-GMC2-2X9W-CGH9

Summary

Details

PoC

Impact

WID-SEC-W-2026-2865

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