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CVE-2026-77751

Estado: AplazadaAlta (8.8)—

A path traversal vulnerability existed in the handling of MISP object template names during STIX 2 import and MISP-to-STIX 2 export.

MISP object names are passed to PyMISP's object-template resolution mechanism, which constructs a filesystem path by joining the configured MISP object-template directory, the object name, and definition.json. An object name originating from untrusted STIX or MISP content was not sufficiently restricted before being used in this filesystem path.

An attacker able to supply a crafted object name containing path separators or traversal sequences such as ../ could therefore cause template resolution to escape the expected template directory and attempt to load a definition.json file from another location accessible to the process.

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During STIX 2 import, an attacker-controlled x_misp_name from a custom STIX object could directly reach this template-resolution mechanism.

The issue could also become persistent. A malicious object name stored in a MISP event could later be processed again during STIX 2 export. Consequently, content originally introduced in one security context could trigger filesystem access later when the event is exported by a process operating with different or greater privileges.

If a suitable definition.json file exists outside the intended template directory, its contents may be interpreted as a MISP object template and fields from that file copied into the converted object. This can result in unintended disclosure of locally accessible data represented by the template file and modification of the resulting object's metadata or semantics.

The patches introduce strict validation of object-template names. Valid names are restricted to a single path component containing letters, digits, hyphens, or underscores. Names that do not meet these requirements are replaced with the generic unknown-template name before reaching PyMISP template resolution. The original rejected name is preserved in the object's comment and a warning is generated, preventing traversal while retaining the source information.

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.

Path traversal en importación STIX (AV:N/PR:N/UI:N) permite lectura de archivos locales fuera del directorio de plantillas. La modificación de metadatos del objeto implica manipulación de datos.

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

Vulnerability ScanningRestrict File and Directory PermissionsPrivileged Account ManagementRemote Data StorageNetwork SegmentationLimit Access to Resource Over Network

Tecnologías afectadas (2)

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

Misp — MispAIPymisp — PymispAI

CWE

Referencias

JSON original (NVD)

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  "id": "CVE-2026-77751",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-77751",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
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          "version": "2.0.3",
          "timestamp": "2026-08-25T19:08:15.945042Z"
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          "Automatable": "NOT_DEFINED",
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "exploitMaturity": "NOT_DEFINED",
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          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
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      "source": "5a6e4751-2f3f-4070-9419-94fb35b644e8",
      "affectedData": [
        {
          "repo": "https://github.com/MISP/misp-stix/",
          "vendor": "misp",
          "product": "misp-stix",
          "versions": [
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              "status": "affected",
              "version": "0",
              "versionType": "semver",
              "lessThanOrEqual": "2026.7.8"
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  "published": "2026-08-21T10:16:39.210",
  "references": [
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      "url": "https://github.com/MISP/misp-stix/commit/a0f54070",
      "source": "5a6e4751-2f3f-4070-9419-94fb35b644e8"
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    {
      "url": "https://github.com/MISP/misp-stix/commit/a8b6808d",
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  "vulnStatus": "Deferred",
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      "description": [
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  "descriptions": [
    {
      "lang": "en",
      "value": "A path traversal vulnerability existed in the handling of MISP object template names during STIX 2 import and MISP-to-STIX 2 export.\n\nMISP object names are passed to PyMISP's object-template resolution mechanism, which constructs a filesystem path by joining the configured MISP object-template directory, the object name, and definition.json. An object name originating from untrusted STIX or MISP content was not sufficiently restricted before being used in this filesystem path.\n\nAn attacker able to supply a crafted object name containing path separators or traversal sequences such as ../ could therefore cause template resolution to escape the expected template directory and attempt to load a definition.json file from another location accessible to the process.\n\nDuring STIX 2 import, an attacker-controlled x_misp_name from a custom STIX object could directly reach this template-resolution mechanism.\n\nThe issue could also become persistent. A malicious object name stored in a MISP event could later be processed again during STIX 2 export. Consequently, content originally introduced in one security context could trigger filesystem access later when the event is exported by a process operating with different or greater privileges.\n\nIf a suitable definition.json file exists outside the intended template directory, its contents may be interpreted as a MISP object template and fields from that file copied into the converted object. This can result in unintended disclosure of locally accessible data represented by the template file and modification of the resulting object's metadata or semantics.\n\nThe patches introduce strict validation of object-template names. Valid names are restricted to a single path component containing letters, digits, hyphens, or underscores. Names that do not meet these requirements are replaced with the generic unknown-template name before reaching PyMISP template resolution. The original rejected name is preserved in the object's comment and a warning is generated, preventing traversal while retaining the source information."
    }
  ],
  "lastModified": "2026-08-26T16:49:18.760",
  "sourceIdentifier": "5a6e4751-2f3f-4070-9419-94fb35b644e8"
}