Astro: Server island encrypted parameters vulnerable to cross-component replay
Exact source revision recorded 24 Oct 2026 13:17:17 UTC. It does not establish the source's current position. Latest evidence.
osv · GHSA-xr5h-phrj-8vxv
Published### Impact Astro versions prior to 6.1.10 used AES-GCM encryption to protect the confidentiality and integrity of server island props and slots parameters, but did not bind the ciphertext to its intended component or parameter type. An attacker could replay one component's encrypted props (`p`) value as another component's slots (`s`) value, or vice versa. Since slots contain raw unescaped HTML while props may contain user-controlled values, this could lead to XSS in applications that meet **all** of the following conditions: - The application uses server islands - Two different server island components share the same key name for a prop and a slot - An attacker has full control over the value of the overlapping prop (requires a dynamically rendered page) These conditions are very unlikely to occur in real-world production applications. ### Patches This has been patched in **[email protected]**. The fix binds each encrypted parameter to its target component and purpose using AES-GCM authenticated additional data (AAD). Each ciphertext now includes context like `props:IslandName` or `slots:IslandName`, so encrypted data for one component cannot be replayed against a different component, and encrypted props cannot be reused as slots. ### References - Fix PR: https://github.com/withastro/astro/pull/16457 - Example demonstrating the vulnerability: https://github.com/CyberSecurityAustria/ACSC2026-web-astronomical
- Source published
- 13 May 2026 01:36:39 UTC
- Source modified
- 14 May 2026 20:52:35 UTC
- Observed here
- 24 Oct 2026 13:17:17 UTC
- Source terms
- GitHub Advisory Database · CC-BY-4.0
Original source record · Cite this exact observation · Complete original publisher JSON
This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.
CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:P
Publisher rating · LOW