Insertion of Sensitive Information Into Sent Data Affecting next package, versions >=13.0.0 <15.5.21>=16.0.0 <16.2.11

next is a react framework.

Affected versions of this package are vulnerable to Insertion of Sensitive Information Into Sent Data in action-handler.ts and action-utils.ts. An attacker can enumerate internal Server Action IDs by sending crafted Next-Action requests or probing client-served artifacts that reference those IDs. This exposes the presence of internal server functions and enables endpoint discovery on apps that use Server Actions, increasing the risk of further abuse when combined with other weaknesses.

Notes

• Publicly served client artifacts can reveal the full Server Action ID format, so the disclosure is not limited to active probing with Next-Action; attackers can also recover candidate IDs from browser-delivered chunks and manifests in apps that ship Server Actions.
• The advisory also covers use cache endpoints exposed through the same App Router server-function machinery, not just use server actions.

Workarounds

• Never assume authentication at the use cache or use server boundary; authenticate inside the Server Action or cache boundary itself so unauthenticated users cannot reach the internal endpoint.

• GitHub Commit
• GitHub Commit
• Maintainer's Advisory