What’s Vulnerable › Vulnerabilities

CVE-2026-100723: vm2 before 3.12.2 Memory Disclosure via zlib Buffer Pool

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-27 · updated 2026-10-01
• Weakness: CWE-200

Description

vm2 before 3.12.2 does not apply its Buffer backing-store ownership invariant (byteOffset === 0 and buffer.byteLength === length) to Buffers returned from host builtin modules. When an application explicitly exposes Node's zlib module through NodeVM's builtin allowlist (require: { builtin: ['zlib'] }), zlib.deflateSync can return a Buffer backed by Node's shared small-buffer pool whose .buffer is the entire pool. Untrusted guest code can construct a full-width view of that ArrayBuffer (Buffer.from(result.buffer, 0, result.buffer.byteLength)) to read and modify bytes belonging to unrelated host buffers, disclosing and corrupting host-realm memory across the sandbox boundary.

Affected products

• patriksimek vm2: before 3.12.2 — fixed in 3.12.2

How to fix

Upgrade to a fixed version: patriksimek vm2 3.12.2. Check the vendor advisory for mitigations.

References

• https://github.com/patriksimek/vm2/commit/4f2508abeb252aa86eb6761c78b3b000248fb089
• https://github.com/patriksimek/vm2/commit/5214b02ef13b82497fcb917b45320dfd014ffd09
• https://github.com/patriksimek/vm2/security/advisories/GHSA-489w-w794-jq94
• https://www.vulncheck.com/advisories/vm2-before-3.12.2-memory-disclosure-via-zlib-buffer-pool
• https://github.com/patriksimek/vm2/security/advisories/GHSA-489w-w794-jq94

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