Vulnerability-Lookup

CVE-2026-74755 (GCVE-0-2026-74755)

Vulnerability from cvelistv5 – Published: 2026-10-21 11:45 – Updated: 2026-10-30 17:56

Title

Apache bRPC: Integer Underflow in mcpack2pb Parser Leading to Denial of Service

Summary

An integer underflow in the mcpack2pb component of Apache bRPC (version < 1.18.0) on all platforms allows remote attackers to crash a bRPC server by sending a request containing a string field with a zero value_size. The UnparsedValue::as_string() function computes `_size - 1` without validating `_size`; when value_size is 0 the expression underflows to SIZE_MAX, resize() throws std::length_error, and because the exception is not caught on the request parsing path the process aborts (SIGABRT). Root Cause: In src/mcpack2pb/parser.cpp, UnparsedValue::as_string() resizes the output string to `_size - 1`, where `_size` is the value_size of a string field taken directly from the network data. A value_size of 0 underflows the unsigned size_t, and the subsequent resize() throws an exception that is not caught. Affected Scenarios: bRPC servers that accept nshead frames wired to the ubrpc mcpack2 adaptor (for example the NsheadService + UbrpcMcpack2Adaptor deployment pattern) can be crashed by a single unauthenticated request. Stock open-source bRPC registers the ubrpc/nshead_mcpack protocols as client-only, so default server configurations are not affected. How to Fix: 1. Upgrade bRPC to a version that includes this fix. 2. Apply the patch in PR https://github.com/apache/brpc/pull/3450

Severity

7.5 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-30 17:56 UTC

CWE

CWE-191 - Integer Underflow (Wrap or Wraparound)

Assigner

apache CNA under the mitre root

CNA scorecard B 76/100 over 1236 records in the last 180 days details

References

1 reference

URL	Tags
https://lists.apache.org/thread/2pf15ojj0vr7rtx95…	vendor-advisory

Impacted products

1 product

Vendor	Product	Version	CPE status
Apache Software Foundation	Apache bRPC	Affected: 0 , < 1.18.0 (semver)	guessed

Credits

Feng Zhijie (Independent security researcher)

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-74755

Vulnerability from fkie_nvd - Published: 2026-10-21 12:17 - Updated: 2026-10-30 18:18

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security@apache.org	https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb

Impacted products

	Vendor	Product	Version

JSON

To clipboard

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    {
      "lang": "es",
      "value": "Una vulnerabilidad de desbordamiento por entero en el componente mcpack2pb de Apache bRPC (versi\u00f3n anterior a la 1.18.0) en todas las plataformas permite a atacantes remotos bloquear un servidor bRPC enviando una solicitud que contiene un campo de cadena con un value_size igual a cero. La funci\u00f3n UnparsedValue::as_string() calcula \u201c_size - 1\u201d sin validar \u201c_size\u201d; cuando value_size es 0 la expresi\u00f3n desborda a SIZE_MAX, resize() lanza std::length_error y, como la excepci\u00f3n no se captura en la ruta de an\u00e1lisis de la solicitud, el proceso aborta (SIGABRT).\\n\\nCausa ra\u00edz:\\nEn src/mcpack2pb/parser.cpp, UnparsedValue::as_string() redimensiona la cadena de salida a \u201c_size - 1\u201d, donde \u201c_size\u201d es el value_size de un campo de cadena tomado directamente de los datos de la red. Un value_size de 0 desborda el size_t sin signo, y el posterior resize() lanza una excepci\u00f3n que no se captura.\\n\\nEscenarios afectados:\\nLos servidores bRPC que aceptan tramas nshead conectadas al adaptador ubrpc mcpack2 (por ejemplo, el patr\u00f3n de despliegue NsheadService + UbrpcMcpack2Adaptor) pueden ser bloqueados por una \u00fanica solicitud no autenticada. La versi\u00f3n de c\u00f3digo abierto de bRPC registra los protocolos ubrpc/nshead_mcpack como solo cliente, por lo que las configuraciones de servidor predeterminadas no se ven afectadas.\\n\\nC\u00f3mo corregir:\\n1. Actualizar bRPC a una versi\u00f3n que incluya esta correcci\u00f3n.  \\n2. Aplicar el parche en PR\u00a0https://github.com/apache/brpc/pull/3450"
    }
  ],
  "id": "CVE-2026-74755",
  "lastModified": "2026-10-30T18:18:12.603",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-74755",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-10-30T17:56:37.339174Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-10-21T12:17:22.550",
  "references": [
    {
      "source": "security@apache.org",
      "url": "https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb"
    }
  ],
  "sourceIdentifier": "security@apache.org",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-191"
        }
      ],
      "source": "security@apache.org",
      "type": "Secondary"
    }
  ]
}

GHSA-9644-97M2-4FC3

Vulnerability from github – Published: 2026-10-21 12:31 – Updated: 2026-10-30 18:32

Details

Root Cause: In src/mcpack2pb/parser.cpp, UnparsedValue::as_string() resizes the output string to _size - 1, where _size is the value_size of a string field taken directly from the network data. A value_size of 0 underflows the unsigned size_t, and the subsequent resize() throws an exception that is not caught.

Affected Scenarios: bRPC servers that accept nshead frames wired to the ubrpc mcpack2 adaptor (for example the NsheadService + UbrpcMcpack2Adaptor deployment pattern) can be crashed by a single unauthenticated request. Stock open-source bRPC registers the ubrpc/nshead_mcpack protocols as client-only, so default server configurations are not affected.

How to Fix: 1. Upgrade bRPC to a version that includes this fix. 2. Apply the patch in PR https://github.com/apache/brpc/pull/3450

Severity

7.5 (High)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Show details on source website

JSON

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74755"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-191"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-21T12:17:22Z",
    "severity": "HIGH"
  },
  "details": "An integer underflow in the mcpack2pb component of Apache bRPC (version \u003c 1.18.0) on all platforms allows remote attackers to crash a bRPC server by sending a request containing a string field with a zero value_size. The UnparsedValue::as_string() function computes `_size - 1` without validating `_size`; when value_size is 0 the expression underflows to SIZE_MAX, resize() throws std::length_error, and because the exception is not caught on the request parsing path the process aborts (SIGABRT).\n\nRoot Cause:\nIn src/mcpack2pb/parser.cpp, UnparsedValue::as_string() resizes the output string to `_size - 1`, where `_size` is the value_size of a string field taken directly from the network data. A value_size of 0 underflows the unsigned size_t, and the subsequent resize() throws an exception that is not caught.\n\nAffected Scenarios:\nbRPC servers that accept nshead frames wired to the ubrpc mcpack2 adaptor (for example the NsheadService + UbrpcMcpack2Adaptor deployment pattern) can be crashed by a single unauthenticated request. Stock open-source bRPC registers the ubrpc/nshead_mcpack protocols as client-only, so default server configurations are not affected.\n\nHow to Fix:\n1. Upgrade bRPC to a version that includes this fix.\n2. Apply the patch in PR\u00a0 https://github.com/apache/brpc/pull/3450",
  "id": "GHSA-9644-97m2-4fc3",
  "modified": "2026-10-30T18:32:20Z",
  "published": "2026-10-21T12:31:11Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74755"
    },
    {
      "type": "WEB",
      "url": "https://lists.apache.org/thread/2pf15ojj0vr7rtx95677kgtl1mx3gdgb"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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CVE-2026-74755 (GCVE-0-2026-74755)

FKIE_CVE-2026-74755

GHSA-9644-97M2-4FC3

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