GHSA-FWWW-CP23-7F5G

Vulnerability from github – Published: 2026-08-28 17:10 – Updated: 2026-08-28 17:10
VLAI
Summary
Yamcs's WebSocket subscription handlers omit the privilege checks their REST siblings enforce
Details

Asset / scope: Yamcs 5.12.7 WebSocket topics (packets, algorithm-status, mdb-changes)

Summary

Several WebSocket subscription handlers do not perform the privilege check that their REST counterparts enforce, so a principal subscribing over WebSocket receives data the REST API would have scoped or denied.

Root cause

  • packets (PacketsApi.subscribePackets) performs no ReadPacket check, while the REST siblings do (listPackets:128, streamPackets:256, subscribeContainers:538). A principal with a narrow ReadPacket scope receives the raw binary of all TM packets on the processor.
  • algorithm-status (ProcessingApi.subscribeAlgorithmStatus) performs no check, while REST getAlgorithmStatus enforces checkObjectPrivileges(ReadAlgorithm, ...) (:467).
  • mdb-changes (MdbOverrideApi.subscribeMdbChanges) performs no check, while base MDB reads require GetMissionDatabase.

Remediation

Bring each WebSocket subscription handler to parity with its REST sibling's privilege check (ReadPacket, ReadAlgorithm, GetMissionDatabase). This is the same declarative fail-closed fix as Report 1.

Supporting material

Subsystem source audit of the WS-vs-REST authorization parity. Available on request.

--

Disclosure and credit

This was found by Cipher / Causal Security - https://causalsecurity.com/. We are coordinating disclosure via this report and request CVEs where you agree they qualify. We propose the 90-day window stated in your security policy. We might publish a write-up after a fix and the agreed window.

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Show details on source website
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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.12.7"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.yamcs:yamcs-core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "5.12.8"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 5.13.1"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.yamcs:yamcs-core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.13.0"
            },
            {
              "fixed": "5.13.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55545"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-862"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-28T17:10:26Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "**Asset / scope:** Yamcs 5.12.7 WebSocket topics (`packets`, `algorithm-status`, `mdb-changes`)\n\n## Summary\n\nSeveral WebSocket subscription handlers do not perform the privilege check that their REST counterparts\nenforce, so a principal subscribing over WebSocket receives data the REST API would have scoped or denied.\n\n## Root cause\n\n- `packets` (`PacketsApi.subscribePackets`) performs no `ReadPacket` check, while the REST siblings do\n  (`listPackets:128`, `streamPackets:256`, `subscribeContainers:538`). A principal with a narrow\n  `ReadPacket` scope receives the raw binary of all TM packets on the processor.\n- `algorithm-status` (`ProcessingApi.subscribeAlgorithmStatus`) performs no check, while REST\n  `getAlgorithmStatus` enforces `checkObjectPrivileges(ReadAlgorithm, ...)` (`:467`).\n- `mdb-changes` (`MdbOverrideApi.subscribeMdbChanges`) performs no check, while base MDB reads require\n  `GetMissionDatabase`.\n\n## Remediation\n\nBring each WebSocket subscription handler to parity with its REST sibling\u0027s privilege check\n(`ReadPacket`, `ReadAlgorithm`, `GetMissionDatabase`). This is the same declarative fail-closed fix as\nReport 1.\n\n## Supporting material\n\nSubsystem source audit of the WS-vs-REST authorization parity. Available on request.\n\n--\n\n## Disclosure and credit\n\nThis was found by Cipher / Causal Security - https://causalsecurity.com/. We are coordinating disclosure\nvia this report and request CVEs where you agree they qualify. We propose the 90-day window stated in your\nsecurity policy. We might publish a write-up after a fix and the agreed window.",
  "id": "GHSA-fwww-cp23-7f5g",
  "modified": "2026-08-28T17:10:26Z",
  "published": "2026-08-28T17:10:26Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/yamcs/yamcs/security/advisories/GHSA-fwww-cp23-7f5g"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yamcs/yamcs/commit/0691731846c5a0aca81b88fabbd2cd51d56fe076"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yamcs/yamcs/commit/12864af555e6ca4941b01c1f1217859cc0492ce0"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/yamcs/yamcs"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yamcs/yamcs/releases/tag/yamcs-5.12.8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/yamcs/yamcs/releases/tag/yamcs-5.13.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Yamcs\u0027s WebSocket subscription handlers omit the privilege checks their REST siblings enforce"
}



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