{"id":100784,"date":"2021-07-17T22:22:35","date_gmt":"2021-07-17T20:22:35","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare"},"modified":"2021-07-17T22:22:35","modified_gmt":"2021-07-17T20:22:35","slug":"uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare","status":"publish","type":"post","link":"https:\/\/prohoster.info\/en\/blog\/news\/uyazvimost-v-cdnjs-pozvolivshaya-vypolnit-kod-na-serverah-cloudflare","title":{"rendered":"A vulnerability in cdnjs that allowed code execution on Cloudflare servers","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

A critical vulnerability has been identified in the Cloudflare content delivery network cdnjs, which is intended to accelerate the delivery of JavaScript libraries, allowing arbitrary code execution on the CDN servers. The severity of the issue is exacerbated by the fact that approximately 12.7% of websites on the internet utilize the service for loading JavaScript libraries, and compromising the infrastructure allows for the replacement of libraries served by any of these sites. <\/p>\n

The cdnjs service loads packages from Git or NPM repositories, allowing any website to use Cloudflare's content delivery network for free to speed up the loading of JavaScript libraries. An examination of the cdnjs component code published on GitHub revealed that the standard archive\/tar module in Go is used for unpacking NPM packages in tgz archives, which outputs the file list as is, without normalizing paths. In cases where the script unpacks content based on the given list, the presence of files like «..\\\/..\\\/..\\\/..\\\/..\\\/..\\\/..\\\/tmp\\\/test» in the archive can lead to arbitrary file overwriting in the system, depending on access permissions. <\/p>\n

It was suggested that an attacker could apply to add their library to cdnjs and upload a specially crafted archive containing files with «..\\\/» in the path to the NPM repository. On cdnjs servers, an «autoupdate» operation is periodically performed, during which the handler downloads new versions of the proposed library and unpacks its contents. Using files with «..\\\/» paths, the attacker could achieve overwriting of service script files and execute their own code on the system. server<\/a> which the unpacking was performed. <\/p>\n

In the case of updates being loaded from Git, it was found that the update-loading handler did not take symbolic links into account when copying files from Git. This feature allowed for the reading of any files with server<\/a> by adding symbolic links in Git. <\/p>\n

Experiments with the demonstration of a cdnjs hack for a bounty on HackerOne began with testing a hypothesis regarding file reading. A symbolic link test.js was added to the Git repository of the CDN-served JavaScript library, pointing to the file \/proc\/self\/maps. After a new version of the library was published, the update handler processed this repository and published the specified file in cdnjs (test.js was created as a symbolic link and when this file was requested, the content of \/proc\/self\/maps was returned). <\/p>\n

By substituting a symbolic link to the file \/proc\/self\/environ, the author of the study noticed that the returned data contained the values of the environment variables GITHUB_REPO_API_KEY and WORKERS_KV_API_TOKEN. The first variable held the API key for write access to the robocdnjs repository on GitHub. The second variable stored the token for the KV store in cdnjs. Using the obtained information, an attacker could make changes to cdnjs and completely compromise the infrastructure.
\n
Source: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

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