vm2: NodeVM zlib Buffers expose pooled host memory across the VM boundary

Why it is Yellow

• CVSS 7.5 high
• Remotely exploitable without logging in
• On your watchlist: npm

Affected packages

References

• https://github.com/advisories/GHSA-489w-w794-jq94
• https://github.com/patriksimek/vm2/security/advisories/GHSA-489w-w794-jq94
• https://github.com/patriksimek/vm2/commit/4f2508abeb252aa86eb6761c78b3b000248fb089
• https://github.com/patriksimek/vm2/commit/5214b02ef13b82497fcb917b45320dfd014ffd09
• https://github.com/patriksimek/vm2/commit/9596bf5e7d8de7351d675ff4f5293b72157202d4
• https://github.com/patriksimek/vm2/releases/tag/v3.12.2
• https://www.vulncheck.com/advisories/vm2-before-3.12.2-memory-disclosure-via-zlib-buffer-pool
• https://github.com/advisories/GHSA-489w-w794-jq94

Original 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.