Linode Safety Digest July 3-July 9, 2023


On this week’s digest, we talk about two vital vulnerabilities in Mastodon.

Mastodon Safety Advisory


Mastodon is a free, open supply, and widely-used decentralized social community with microblogging options. It’s considered as an open supply and decentralized different to Twitter. Mastodon is run by way of independently managed nodes hosted by completely different entities on cloud internet hosting platforms, together with Linode.


Mastodon lately launched its new variations earlier this week, which repair a number of vulnerabilities, together with two vital vulnerabilities: CVE-2023-36460 and CVE-2023-36459.

CVE-2023-36460: Arbitrary File Creation Via Media Attachments

This vulnerability, tracked as CVE-2023-36460 and described beneath GHSA-9928, permits an attacker to create and overwrite recordsdata in any arbitrary location to which the put in Mastodon occasion has entry.

Susceptible variations of Mastodon (from model 3.5.0 and previous to variations 3.5.9, 4.0.5, and 4.1.3) use exterior inputs to assemble a path title with out correctly sanitizing and neutralizing the particular parts inside the path title. This exterior enter is meant to establish a file or listing beneath a restricted listing. Nonetheless, it isn’t restricted or sanitized to solely resolve inside this specified listing, thus permitting for entry and writing outdoors the restricted listing by way of listing traversal. Such an exploit can result in devastating penalties starting from Denial-of-Service to Distant Code Execution on the Mastodon server.

The vulnerability has a excessive influence and is rated to have a vital severity, as any person who can put up to a Mastodon server can exploit this vulnerability. Moreover, Mastodon is a social media platform, and the variety of customers who could make posts and run exploits may be very excessive.

CVE-2023-36459: XSS by oEmbed preview playing cards

This vulnerability, tracked as CVE-2023-36459 and described beneath GHSA-ccm4, is a Cross-Website Scripting (XSS) vulnerability that permits an attacker to craft a Mastodon oEmbed information to incorporate arbitrary HTML in oEmbed preview playing cards leading to varied dangers related to a person interacting with an internet site with untrusted supply code.

Susceptible variations of Mastodon (from model 1.3 and previous to variations 3.5.9, 4.0.5, and 4.1.3) enable an attacker to bypass the HTML sanitization course of utilizing oEmbed information. These variations of Mastodon don’t accurately neutralize user-controllable enter in oEmbed preview playing cards earlier than it’s positioned in output as part of an online web page served to different customers. Thus, an attacker-controlled HTML is served to customers. This exploit introduces a vector for XSS payloads which, when interacted with by a person, can run untrusted malicious code within the person’s browser and machine.

The vulnerability has a excessive influence and important severity, as any person who can create oEmbed information on a mastodon server can exploit this vulnerability. Moreover, all members of an contaminated server are vulnerable to an assault.

  • Replace your hosted Mastodon cases to variations 4.1.3, 4.0.5, or 3.5.9
  • Ensure the Mastodon servers you go to are updated with the newest model

Word: Mastodon will be hosted on Linodes by way of guide set up and can also be supplied as a One Click on Market App. Nonetheless, these cases should not managed or maintained by Linode. It’s incumbent upon Linode customers to grasp the dangers and hold the put in software program up-to-date. For extra info, try our Mastodon Market App Deployment Information.


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