GitHub has mounted a race condition vulnerability in its repository creation and consumer renaming operations that would have enabled risk actors to carry out what is called a repojacking assault.
Discovered and disclosed by researchers from Checkmarx, had the flaw been exploited it might have been used to take management of code repositories and hijack them to distribute malicious code. It might even have had dangerous implications for the reputations of those that fell sufferer to it.
“Repojacking is a method the place an attacker takes management of a GitHub repository by exploiting a logical flaw that renders renamed customers weak,” wrote Elad Rapoport of Checkmarx.
“The attacker hijacks a professional, usually fashionable, namespace on GitHub. A namespace is the mixture of the username and repo identify, for instance: example-user/example-repo.”
Namespaces on GitHub turn into weak to repojacking when the unique username is modified utilizing the “consumer rename” function. When a GitHub consumer renames themselves, GitHub doesn’t arrange redirects for his or her previous profile web page or Pages websites, however does create redirects for his or her repositories. Customers are made conscious of this by way of a pop-up throughout the course of.
Sadly, in doing so, the previous username additionally turns into out there for anyone else to assert, so as soon as the consumer has been efficiently renamed, a malicious actor can declare their previous username, open a repo beneath the matching repo identify, and hijack the namespace.
Different flaws on this course of have beforehand been recognized and glued, and GitHub did have safety measures out there – notably retiring fashionable repositories (these with greater than 100 clones on the time of renaming) in order that the username couldn’t be taken.
Nevertheless, Rapoport discovered he was capable of bypass these fixes by benefiting from a race situation between the creation of a repository and the renaming of a username, by virtually concurrently doing each – utilizing an API request for repository creation and a renamed request interception for the username change.
“Profitable exploitation permits the takeover of fashionable code packages in a number of bundle managers, together with ‘Packagist,’ ‘Go,’ ‘Swift’ and extra,” he mentioned. “We now have recognized over 4,000 packages in these bundle managers utilizing renamed usernames and are vulnerable to being weak to this system in case a brand new bypass is discovered. Of those packages in danger, a whole lot of them have garnered over 1,000 stars on GitHub.
“As well as, exploiting this bypass may also end in a takeover of fashionable GitHub actions, that are additionally consumed by specifying a GitHub namespace. Poisoning a well-liked GitHub motion might result in main provide chain assaults with important repercussions.”
Though this repojacking challenge has been mounted, it’s the fourth one discovered up to now couple of years – three in 2022 alone – and Rapoport mentioned it spoke to persistent dangers related to the favored repository namespace retirement mechanism.
“Many GitHub customers, together with customers that management fashionable repositories and packages, select to make use of the ‘consumer rename’ function GitHub presents,” he mentioned. “For that motive, the try to bypass the ‘fashionable repository namespace retirement’ stays a horny assault level for provide chain attackers with the potential to trigger substantial damages.”
Despite the repair, Checkmarx is recommending that customers keep away from utilizing retired namespaces to minimise their assault floor, and ensure there are not any code dependencies which will go away a GitHub repository weak. It presents its personal open supply instrument, Chainjacking, which may help with this.
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