Astro, a web framework, used AES-GCM encryption to protect server island props and slots parameters but failed to bind ciphertext to its intended component or parameter type. This allowed an attacker to replay encrypted props as slots or vice versa, potentially causing XSS when slots contain raw unescaped HTML and props contain user-controlled values. The issue arises when two different server island components share the same key name for a prop and a slot, and the attacker controls the overlapping prop value on a dynamically rendered page. The vulnerability is tracked as CVE-2026-45028 and is fixed in Astro version 6.1.10.

An attacker with control over certain prop values in a vulnerable Astro application could exploit this flaw to perform cross-site scripting (XSS) attacks by replaying encrypted data between props and slots. This could lead to injection of malicious HTML or scripts in the application. The CVSS score is low (2.9), reflecting limited impact and exploitation complexity.

Upgrade Astro to version 6.1.10 or later, where this vulnerability is fixed. Since the vendor advisory indicates the issue is resolved in 6.1.10, applying this official fix is the recommended remediation. No additional mitigation steps are specified.