Version Details and Security Vulnerabilities

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);

lodash versions prior to 4.17.21 are vulnerable to Command Injection via the template function.

Versions of lodash before 4.17.12 are vulnerable to Prototype Pollution. The function defaultsDeep allows a malicious user to modify the prototype of Object via {constructor: {prototype: {...}}} causing the addition or modification of an existing property that will exist on all objects.

Recommendation

Update to version 4.17.12 or later.

Versions of lodash prior to 4.17.19 are vulnerable to Prototype Pollution. The functions pick, set, setWith, update, updateWith, and zipObjectDeep allow a malicious user to modify the prototype of Object if the property identifiers are user-supplied. Being affected by this issue requires manipulating objects based on user-provided property values or arrays.

This vulnerability causes the addition or modification of an existing property that will exist on all objects and may lead to Denial of Service or Code Execution under specific circumstances.

A vulnerability was found in the minimatch package. This flaw allows a Regular Expression Denial of Service (ReDoS) when calling the braceExpand function with specific arguments, resulting in a Denial of Service.

Impact

A bad regular expression is generated any time you have two parameters within a single segment, separated by something that is not a period (.). For example, /:a-:b.

Patches

For users of 0.1, upgrade to 0.1.10. All other users should upgrade to 8.0.0.

These versions add backtrack protection when a custom regex pattern is not provided:

• 0.1.10
• 1.9.0
• 3.3.0
• 6.3.0

They do not protect against vulnerable user supplied capture groups. Protecting against explicit user patterns is out of scope for old versions and not considered a vulnerability.

Version 7.1.0 can enable strict: true and get an error when the regular expression might be bad.

Version 8.0.0 removes the features that can cause a ReDoS.

Workarounds

All versions can be patched by providing a custom regular expression for parameters after the first in a single segment. As long as the custom regular expression does not match the text before the parameter, you will be safe. For example, change /:a-:b to /:a-:b([^-/]+).

If paths cannot be rewritten and versions cannot be upgraded, another alternative is to limit the URL length. For example, halving the attack string improves performance by 4x faster.

Details

Using /:a-:b will produce the regular expression /^\/([^\/]+?)-([^\/]+?)\/?$/. This can be exploited by a path such as /a${'-a'.repeat(8_000)}/a. OWASP has a good example of why this occurs, but the TL;DR is the /a at the end ensures this route would never match but due to naive backtracking it will still attempt every combination of the :a-:b on the repeated 8,000 -a.

Because JavaScript is single threaded and regex matching runs on the main thread, poor performance will block the event loop and can lead to a DoS. In local benchmarks, exploiting the unsafe regex will result in performance that is over 1000x worse than the safe regex. In a more realistic environment using Express v4 and 10 concurrent connections, this translated to average latency of ~600ms vs 1ms.

References

• OWASP
• Detailed blog post

Versions of the package semver before 7.5.2 on the 7.x branch, before 6.3.1 on the 6.x branch, and all other versions before 5.7.2 are vulnerable to Regular Expression Denial of Service (ReDoS) via the function new Range, when untrusted user data is provided as a range.

Impact

passing untrusted user input - even after sanitizing it - to SendStream.redirect() may execute untrusted code

Patches

this issue is patched in send 0.19.0

Workarounds

users are encouraged to upgrade to the patched version of express, but otherwise can workaround this issue by making sure any untrusted inputs are safe, ideally by validating them against an explicit allowlist

Details

successful exploitation of this vector requires the following:

1. The attacker MUST control the input to response.redirect()
2. express MUST NOT redirect before the template appears
3. the browser MUST NOT complete redirection before:
4. the user MUST click on the link in the template