Type Confusion in start-server-core - #VU139898
Published: July 28, 2026
Vulnerability identifier: #VU139898
CSH Severity: Low
CVSS v4.0: 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:U/U:Clear
CVE-ID: N/A
CWE-ID: CWE-843
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: TanStack
Affected software:
start-server-core
start-server-core
Detailed vulnerability description
The vulnerability allows a remote attacker to invoke a different client-referenced server function as a side effect of request deserialization.
The vulnerability exists due to type confusion in the inbound server-function request deserialization logic when processing a crafted JSON request body. A remote attacker can send a specially crafted request body to invoke a sibling client-referenced server function as a side effect of deserialization.
The inner invocation does not re-run request-level middleware, while the target function's per-function middleware chain still executes. Server-only functions cannot be reached through this mechanism.
Remediation
Install security update from vendor's website.