Satori is a library that converts HTML and CSS to SVG. From version 0.0.27 up to but not including 0.33.5, the library fails to escape certain values before embedding them into generated SVG output. A crafted value can be interpreted as SVG markup, potentially injecting executable elements such as <script> or malicious links. The impact is limited to situations where the resulting SVG is rendered in a browser; it can lead to client‑side code execution (XSS) or other manipulation of the user interface.

Vercel’s Satori library version 0.0.27 through 0.33.4 is affected, along with any Vercel Next.js deployments that rely on that version of Satori. The patch is included in Satori 0.33.5 and in Next.js releases starting at 16.3.6.

The CVSS score of 5.3 indicates a moderate risk. EPSS data are not available and the vulnerability is not listed in the CISA KEV catalog. The likely attack vector involves an attacker supplying maliciously crafted HTML or CSS to the Satori conversion process, with the malicious content ultimately rendered in a browser that loads the resulting SVG. Exploitation requires that the SVG be displayed to a user – it does not elevate privileges on the server side.