GitHub Fixes a Private-Package-Names Leak and Serious Authorization Bug

In 2020 Microsoft’s GitHub acquired NPM (makers of the default package manager for Node.js). The company’s web page boasts that npm “is a critical part of the JavaScript community and helps support one of the largest developer ecosystems in the world.”

But now BleepingComputer reports on two security flaws found (and remediated) in its software registry. Names of private npm packages on’s ‘replica’ server (consumed by third-party services) were leaked — but in addition, a second flaw could’ve allowed attackers “to publish new versions of any existing npm package that they do not own or have rights to, due to improper authorization checks.”

In a blog post this week GitHub’s chief security officer explained the details:
During maintenance on the database that powers the public npm replica at, records were created that could expose the names of private packages. This briefly allowed consumers of to potentially identify the names of private packages due to records published in the public changes feed. No other information, including the content of these private packages, was accessible at any time. Package names in the format of @owner/package for private packages created prior to October 20 were exposed between October 21 13:12:10Z UTC and October 29 15:51:00Z UTC. Upon discovery of the issue, we immediately began work on implementing a fix and determining the scope of the exposure. On October 29, all records containing private package names were removed from the replication database. While these records were removed from the service on this date, the data on this service is consumed by third-parties who may have replicated the data elsewhere. To prevent this issue from occuring again, we have made changes to how we provision this public replication database to ensure records containing private package names are not generated during this process.

Second, on November 2 we received a report to our security bug bounty program of a vulnerability that would allow an attacker to publish new versions of any npm package using an account without proper authorization. We quickly validated the report, began our incident response processes, and patched the vulnerability within six hours of receiving the report.

We determined that this vulnerability was due to inconsistent authorization checks and validation of data across several microservices that handle requests to the npm registry. In this architecture, the authorization service was properly validating user authorization to packages based on data passed in request URL paths. However, the service that performs underlying updates to the registry data determined which package to publish based on the contents of the uploaded package file. This discrepancy provided an avenue by which requests to publish new versions of a package would be authorized for one package but would actually be performed for a different, and potentially unauthorized, package. We mitigated this issue by ensuring consistency across both the publishing service and authorization service to ensure that the same package is being used for both authorization and publishing.

This vulnerability existed in the npm registry beyond the timeframe for which we have telemetry to determine whether it has ever been exploited maliciously. However, we can say with high confidence that this vulnerability has not been exploited maliciously during the timeframe for which we have available telemetry, which goes back to September 2020.
BleepingComputer adds:
Both announcements come not too long after popular npm libraries, ‘ua-parser-js,’ ‘coa,’ and ‘rc‘ were hijacked in a series of attacks aimed at infecting open source software consumers with trojans and crypto-miners. These attacks were attributed to the compromise of npm accounts [1, 2] belonging to the maintainers behind these libraries.

None of the maintainers of these popular libraries had two-factor authentication (2FA) enabled on their accounts, according to GitHub. Attackers who can manage to hijack npm accounts of maintainers can trivially publish new versions of these legitimate packages, after contaminating them with malware. As such, to minimize the possibility of such compromises from recurring in near future, GitHub will start requiring npm maintainers to enable 2FA, sometime in the first quarter of 2022.