It has been discovered that hackers can distribute malicious payloads easily and efficiently through the package repository on the PyPI website by using a simple and troublesome exploit. A JFrog security researcher has discovered a new supply chain attack technique using which they can attack PyPI repositories (Python Package Index) that can be used to hack them. 

Hundreds of thousands of software packages can potentially be affected by this attack technique and countless users could be affected as a result. A technique known as "Revival Hijack," exploits a policy loophole by which attackers may re-register the names of packages that have been removed from PyPI by their original developers and hijack the names themselves once the packages have been removed from PyPI. 

As part of an attack against the Python Package Index (PyPI) registry, a new supply chain attack technique has been uncovered in the wild, which is designed to infiltrate downstream organizations by exploiting the PyPI registry. There is an attack vector called "Revival Hijack" which involves the registration of a new project with a name that matches a package that has been removed from the PyPI platform which may then serve as an attack vector. 

If a threat actor manages to do this, then they will be able to distribute malicious code to developers who pull updates periodically. A software supply chain security firm named JFrog, which specializes in software supply chain security, has codenamed this attack method Revival Hijack, claiming to be able to hijack 22,000 existing PyPI packages, which in turn will result in hundreds of thousands of malicious packages being downloaded. 

There are more than 100,000 downloads or six months' worth of activity on the affected packages and are more susceptible to exploits. A very common technique used by Revival Hijack is to take advantage of the fact that victims are often unknowingly updating once-safe packages without being aware that they have been altered or compromised. Further, CI/CD machines are set up with a mechanism for automatically installing package updates so that they can be applied right away. 

A similar attack technique was discovered by Jfrog earlier this year, which is one of several different attacks that adversaries have been developing in recent years to try and sneak malware into enterprise environments using public code repositories like PyPI, npm, Maven Central, NuGet, and RubyGems, and to steal sensitive data. As a part of these attacks, popular repositories have often been cloned and infected, poisoning artifacts have been used, and leveraged leaked secrets such as private keys and database certificates have been revealed. 

According to JFrog researchers Brian Moussalli and Andrey Polkovnichenko, there is a much higher risk here than in previous software supply chain hacks that relied primarily on typosquatting and human error to distribute malicious code throughout software websites. When a developer decides to delete a project from PyPI, they are given a warning about the potential repercussions that may arise, including the Revival Hijack scenario that could occur. 

The dialogue warns that deleting this project will give the name of the project to anyone else who uses PyPI", so please refrain from doing so. In this scenario, the user will be able to issue new releases under the project name as long as the distribution files have not been renamed to match those from a previously released distribution. According to the motive of the attacker, the "Revival Hijack" attack vector can result in hundreds of thousands of increments as a result of the attack, depending on the motive. 

As far as exploiting this technique is concerned, it can be applied to exploiting abandoned package names to spread malware. Researchers observed this in action with the hijack of the "pingdomv3" package, which was detected by research teams. This package has been given the version number 0.0.0.1 to avoid a dependency confusion attack scenario, in which developer packages would be pulled by pip upgrade commands when they were run as a part of the upgrade process. 

In addition, it is worth noting that Revival Hijack has already been exploited in the wild, by an unknown threat actor called Jinnis who introduced a benign version of a package titled "pingdomv3" on March 30, 2024, just two days after the original package's owner (cheneyyan) removed it from PyPI. There has been a report that says the new developer has released an update containing a Base64-encoded payload, which checks for the presence of the "JENKINS_URL" environment variable, and if it exists, executes an unknown next-stage module retrieved from a remote server after checking for the appearance of the "JENKINS_URL." environment variable. 

Although JFrog proposed this precaution as a preventative measure, over the last three months it has received nearly 200,000 downloads both manually and automatically, proving that the Revival Hijack threat is very real, the security company announced. In making an analysis of this data, JFrog reported that there are outdated jobs and scripts out there that are still searching for the deleted packages, as well as users who manually downloaded these packages due to typosquatting. 

Depending on how the hijacked packages are hijacked, the adversaries may attach a high version number to each package, which will cause the CI/CD systems to automatically download the hijacked packages believing they are the latest version. This will ultimately cause a bug to develop, JFrog explained. As a result of the company's recommendation, PyPI has effectively prohibited the reuse of abandoned package names as well.

Some organizations use PyPI that need to be aware of this attack vector when updating to new versions of the package, JFrog warns. There is a non-public blacklist maintained by PyPI, which prevents certain names from being registered on new projects, but most deleted packages don't make it to that list because there is a non-public blacklist maintained by PyPI. It was due to this that the security firm took indirect measures to mitigate the "Revival Hijack" threat and added the most popular of the deleted and vulnerable packages to an account named security_holding under which they could be monitored. 

As a result of the researchers changing the version numbers of the abandoned packages to 0.0.0.1, they make sure that it does not affect active users while updating the packages. As a result, the package names are preserved and are not susceptible to theft by malicious actors who may want to use them for offensive purposes. The third month later, JFrog discovered that the packages in their repository seemed to have been downloaded by nearly 200,000 people due to automatic scripts or user errors. There are a lot more risks involved in "Revival Hijack" than the standard typosquatting attacks on PyPI. 

This is because users pulling updates for their selected projects for which they have permission do not make mistakes when doing so. It's best to mitigate this threat by utilizing package pinning to stay on a known secure version, verify the integrity of the package, audit its contents, and watch for any changes in package ownership or unusual updates.