CVE-2025-55303: withastro astro · Cross-site Scripting
Affects withastro astroSource CVE Database V5
Not known to be exploited · public detection template (Nuclei) · CVSS 6.9 Medium : upgrade to 4.16.18 when convenient.
Data as of 26 Oct 2026, 12:55 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 4.16.18
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 19 Aug 2025
Detectable: evidence found.
nuclei template: Astro - Unauthorized Third-Party Image Access
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade withastro astro to 4.16.18.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| withastro astro | Affected
| Fixed in
|
AI-suggested
European organizations should promptly upgrade Astro to versions 5.13.2 or 4.16.18 to apply the official fix. In addition, developers should audit their usage of the /_image endpoint to ensure that image URLs are strictly validated and sanitized, disallowing protocol-relative URLs or any input that could bypass domain restrictions. Implementing Content Security Policy (CSP) headers that restrict image sources to trusted domains can provide an additional defense layer. Monitoring web traffic for unusual requests to the /_image endpoint and setting up alerting for anomalous patterns can help detect exploitation attempts early. Organizations should also review their incident response plans to address potential phishing or content spoofing incidents stemming from this vulnerability. Finally, integrating automated security testing into the CI/CD pipeline to detect similar input validation issues can prevent future regressions.
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.