6.0 Medium

GraphQL Tools: Shared legacy executor routes one subscription's results to a different caller

CVE-2026-118666

Cross-tenant subscription data leak in @graphql-tools/executor-legacy-ws: a shared websocket.onmessage is replaced on every subscribe(), and DATA frames are delivered without checking the protocol operation id Report metadata | Field | Value | | --- | --- | | Package | @graphql-tools/executor-legacy-ws (npm, pkg:npm/%40graphql-tools/executor-legacy-ws) | | Repository | https://github.com/ardatan/graphql-tools | | Component | buildWSLegacyExecutor → the returned executor's subscribe(observer) / websocket.onmessage handler | | Vulnerability class | Cross-tenant data leak (subscription results delivered to the wrong caller) | | Verified against | Source at b5d1c36ebb8ed3868260ffee5bbcbb423ad5c1f1 (package version 1.1.33); published npm tarball 1.1.33 with matching source at d304214db06e8a4ce9cb41138f199e3bc6ed36f2; the same behaviour also reproduces on the current release 1.1.35 | | API surface | Public documented API (buildWSLegacyExecutor) | | Affected in default configuration | Yes — ensureWebsocket() reuses an already-OPEN socket (index.ts:35-42), and the socket has a single mutable onmessage property (index.ts:113). No single-operation-only restriction is documented, and the…

Assessment

CVSS: 6 (v4.0)
Severity: Medium
EPSS: 0.00335% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 28 October 2026
Last updated: 28 October 2026
Affected: npm · @graphql-tools/executor-legacy-ws
Weakness: CWE-200

CVSS vectorCVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:N/VA:L/SC:N/SI:N/SA:N

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