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CVE-2026-77658

Estado: Pendiente de análisisAlta (7.8)—

A stack-based buffer overflow vulnerability exists in the Dia diagram editor when processing Network Bus objects from Dia XML project files.

In objects/network/bus.c, bus_load() reads the number of bus handles from the file attribute "bus_handles" using attribute_num_data() without validating an upper bound:

When a bus handle is subsequently moved, bus_handle_moved() allocates two temporary arrays on the stack:

Because num_handles is fully attacker-controlled via the project file, sufficiently large values (for example 262144 or higher) cause g_alloca() to consume more stack space than the default thread stack limit (typically 8 MB on Linux), resulting in stack overflow, SIGSEGV, and potential stack frame / return-address corruption.

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An attacker can embed a Bus object with an excessive bus_handles count in a malicious .dia file. Exploitation requires the victim to open the file in Dia (file dialog, command line, or file association) and trigger handle manipulation (moving a bus handle), which exercises the vulnerable code path.

The identical g_alloca pattern is present in objects/Misc/tree.c (copied from bus.c) and is likely vulnerable to the same class of attack via Tree objects.

Affected versions: Dia 0.98.0 and earlier versions containing this code; issue confirmed on upstream master as of 2026-08-21. Upstream report: https://gitlab.gnome.org/GNOME/dia/-/issues/581

Detalles técnicos trazas, registros y código del informe original
    bus->num_handles = attribute_num_data(attr);

    parallel = (real *)g_alloca(num_handles * sizeof(real));
    perp = (real *)g_alloca(num_handles * sizeof(real));

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

🎯 Técnicas ATT&CK

Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.

Vulnerabilidad de desbordamiento de búfer en archivo local (.dia) que requiere interacción del usuario (abrir archivo y mover control) para corromper la pila y potencialmente ejecutar código.

Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.

🛡️ Mitigaciones ATT&CK que cubren estas técnicas

Restrict Web-Based ContentPrivileged Account ManagementLimit Software InstallationExecution PreventionBehavior Prevention on EndpointDisable or Remove Feature or Program

Tecnologías afectadas (1)

⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.

DIA — DIAAI

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-77658",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-77658",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-08-26T13:09:44.563034Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "patrick@puiterwijk.org",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.8,
          "attackVector": "LOCAL",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 1.8
      }
    ]
  },
  "affected": [
    {
      "source": "patrick@puiterwijk.org",
      "affectedData": [
        {
          "vendor": "GNOME",
          "product": "Dia",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "versionType": "semver",
              "lessThanOrEqual": "0.98.0"
            }
          ],
          "packageName": "dia",
          "collectionURL": "https://gitlab.gnome.org/GNOME/dia/-/issues/581",
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-08-26T13:19:22.043",
  "references": [
    {
      "url": "https://access.redhat.com/security/cve/CVE-2026-77658",
      "source": "patrick@puiterwijk.org"
    },
    {
      "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2520890",
      "source": "patrick@puiterwijk.org"
    },
    {
      "url": "https://gitlab.gnome.org/GNOME/dia/-/blob/master/objects/network/bus.c",
      "source": "patrick@puiterwijk.org"
    },
    {
      "url": "https://gitlab.gnome.org/GNOME/dia/-/issues/581",
      "source": "patrick@puiterwijk.org"
    }
  ],
  "vulnStatus": "Awaiting Analysis",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "patrick@puiterwijk.org",
      "description": [
        {
          "lang": "en",
          "value": "CWE-121"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "A stack-based buffer overflow vulnerability exists in the Dia diagram editor when processing Network Bus objects from Dia XML project files.\n\nIn objects/network/bus.c, bus_load() reads the number of bus handles from the file attribute \"bus_handles\" using attribute_num_data() without validating an upper bound:\n\n    bus->num_handles = attribute_num_data(attr);\n\nWhen a bus handle is subsequently moved, bus_handle_moved() allocates two temporary arrays on the stack:\n\n    parallel = (real *)g_alloca(num_handles * sizeof(real));\n    perp = (real *)g_alloca(num_handles * sizeof(real));\n\nBecause num_handles is fully attacker-controlled via the project file, sufficiently large values (for example 262144 or higher) cause g_alloca() to consume more stack space than the default thread stack limit (typically 8 MB on Linux), resulting in stack overflow, SIGSEGV, and potential stack frame / return-address corruption.\n\nAn attacker can embed a Bus object with an excessive bus_handles count in a malicious .dia file. Exploitation requires the victim to open the file in Dia (file dialog, command line, or file association) and trigger handle manipulation (moving a bus handle), which exercises the vulnerable code path.\n\nThe identical g_alloca pattern is present in objects/Misc/tree.c (copied from bus.c) and is likely vulnerable to the same class of attack via Tree objects.\n\nAffected versions: Dia 0.98.0 and earlier versions containing this code; issue confirmed on upstream master as of 2026-08-21.\nUpstream report: https://gitlab.gnome.org/GNOME/dia/-/issues/581"
    }
  ],
  "lastModified": "2026-08-28T15:44:39.323",
  "sourceIdentifier": "patrick@puiterwijk.org"
}