CVE-2026-52830

{
  "id": "CVE-2026-52830",
  "sourceIdentifier": "[email protected]",
  "published": "2026-07-02T21:16:56.847",
  "lastModified": "2026-10-25T21:10:00.770",
  "vulnStatus": "Deferred",
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "fast-mcp-telegram is a Telegram MCP Server. Prior to 0.19.1, fast-mcp-telegram validates HTTP Bearer tokens by joining the raw token string into a session-file path. The verifier rejects the exact reserved token telegram, but it does not reject path separators or normalize the path before checking whether the session file exists. A remote HTTP client can therefore authenticate as the default legacy session with a token such as ../fast-mcp-telegram/telegram when the documented default session file ~/.config/fast-mcp-telegram/telegram.session exists. This bypasses the reserved session name control that is intended to prevent HTTP multi-user sessions from colliding with the default stdio or legacy account. With account-prefixed MCP tools enabled, the attacker still sees and calls the prefixed tools for the default account, so the prefix middleware does not stop the session selection bypass. This vulnerability is fixed in 0.19.1."
    },
    {
      "lang": "es",
      "value": "fast-mcp-telegram es un servidor MCP de Telegram. Antes de la versión 0.19.1, fast-mcp-telegram valida los tokens Bearer HTTP uniendo la cadena de token en bruto en una ruta de archivo de sesión. El verificador rechaza el token reservado exacto ’telegram’, pero no rechaza los separadores de ruta ni normaliza la ruta antes de verificar si el archivo de sesión existe. Un cliente HTTP remoto puede, por lo tanto, autenticarse como la sesión heredada predeterminada con un token como .. / fast-mcp-telegram/telegram cuando el archivo de sesión predeterminado documentado ~/.config/fast-mcp-telegram/telegram.session existe. Esto elude el control de nombre de sesión reservado que está destinado a evitar que las sesiones multiusuario HTTP colisionen con la cuenta stdio predeterminada o heredada. Con las herramientas MCP con prefijo de cuenta habilitadas, el atacante todavía ve y llama a las herramientas con prefijo para la cuenta predeterminada, por lo que el middleware de prefijo no detiene la elusión de la selección de sesión. Esta vulnerabilidad se corrige en la versión 0.19.1."
    }
  ],
  "affected": [
    {
      "source": "[email protected]",
      "affectedData": [
        {
          "vendor": "leshchenko1979",
          "product": "fast-mcp-telegram",
          "versions": [
            {
              "version": "< 0.19.1",
              "status": "affected"
            }
          ]
        }
      ]
    }
  ],
  "metrics": {
    "cvssMetricV31": [
      {
        "source": "[email protected]",
        "type": "Secondary",
        "cvssData": {
          "version": "3.1",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L",
          "baseScore": 9.4,
          "baseSeverity": "CRITICAL",
          "attackVector": "NETWORK",
          "attackComplexity": "LOW",
          "privilegesRequired": "NONE",
          "userInteraction": "NONE",
          "scope": "UNCHANGED",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "availabilityImpact": "LOW"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 5.5
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "timestamp": "2026-07-06T14:35:51.099192Z",
          "id": "CVE-2026-52830",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "version": "2.0.3"
        }
      }
    ]
  },
  "weaknesses": [
    {
      "source": "[email protected]",
      "type": "Secondary",
      "description": [
        {
          "lang": "en",
          "value": "CWE-22"
        },
        {
          "lang": "en",
          "value": "CWE-287"
        }
      ]
    }
  ],
  "references": [
    {
      "url": "https://github.com/advisories/GHSA-rxw2-pc8j-vxwm",
      "source": "[email protected]"
    },
    {
      "url": "https://web.archive.org/web/20250926152207/https://github.com/leshchenko1979/fast-mcp-telegram",
      "source": "[email protected]"
    },
    {
      "url": "https://github.com/advisories/GHSA-rxw2-pc8j-vxwm",
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"
    }
  ]
}