Unauthorized third-party images in Astro’s _image endpoint

Vulnerability Description

Astro is a web framework for content-driven websites. In versions of astro before 5.13.2 and 4.16.18, the image optimization endpoint in projects deployed with on-demand rendering allows images from unauthorized third-party domains to be served. On-demand rendered sites built with Astro include an /_image endpoint which returns optimized versions of images. A bug in impacted versions of astro allows an attacker to bypass the third-party domain restrictions by using a protocol-relative URL as the image source, e.g. /_image?href=//example.com/image.png. This vulnerability is fixed in 5.13.2 and 4.16.18.

References

• https://github.com/withastro/astro/security/advisories/GHSA-xf8x-j4p2-f749
• https://github.com/withastro/astro/commit/4d16de7f95db5d1ec1ce88610d2a95e606e83820