FKIE_CVE-2026-26028

Vulnerability from fkie_nvd - Published: 2026-05-20 20:16 - Updated: 2026-07-23 12:10
Severity
6.1 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Summary
CryptPad is an end-to-end encrypted collaborative office suite. In versions prior to 2026.2.0, the HTML sanitizer in Diffmarked.js can be bypassed due to incomplete attribute filtering on restricted tags. The sanitizer validates only the src attribute of <iframe>, <video>, and <audio> elements, leaving all other attributes unchecked. As a result, an attacker can inject arbitrary HTML through srcdoc, completely defeating CryptPad's intended bounce sandboxing and enabling link injection or other interactive content within user-controlled documents. The root cause lies in how the sanitizer classifies and enforces tag restrictions: although it defines both forbidden and restricted tag lists, <iframe> is treated as "restricted" rather than "forbidden." Enforcement then inspects only the src attribute, so pairing a benign blob: src with a malicious srcdoc results in unrestricted rendering. This issue has been fixed in version 2026.2.0.
References
security-advisories@github.comhttps://github.com/cryptpad/cryptpad/releases/tag/2026.2.0
security-advisories@github.comhttps://github.com/cryptpad/cryptpad/security/advisories/GHSA-g2g4-47gv-p72v
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "cryptpad",
          "vendor": "cryptpad",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2026.2.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "CryptPad is an end-to-end encrypted collaborative office suite. In versions prior to 2026.2.0, the HTML sanitizer in Diffmarked.js can be bypassed due to incomplete attribute filtering on restricted tags. The sanitizer validates only the src attribute of \u003ciframe\u003e, \u003cvideo\u003e, and \u003caudio\u003e elements, leaving all other attributes unchecked. As a result, an attacker can inject arbitrary HTML through srcdoc, completely defeating CryptPad\u0027s intended bounce sandboxing and enabling link injection or other interactive content within user-controlled documents. The root cause lies in how the sanitizer classifies and enforces tag restrictions: although it defines both forbidden and restricted tag lists, \u003ciframe\u003e is treated as \"restricted\" rather than \"forbidden.\" Enforcement then inspects only the src attribute, so pairing a benign blob: src with a malicious srcdoc results in unrestricted rendering. This issue has been fixed in version 2026.2.0."
    },
    {
      "lang": "es",
      "value": "CryptPad es una suite ofim\u00e1tica colaborativa cifrada de extremo a extremo. En versiones anteriores a la 2026.2.0, el saneador de HTML en Diffmarked.js puede ser eludido debido a un filtrado incompleto de atributos en etiquetas restringidas. El saneador valida solo el atributo src de los elementos \u003ciframe\u003e, \u003cvideo\u003e y \u003caudio\u003e, dejando todos los dem\u00e1s atributos sin verificar. Como resultado, un atacante puede inyectar HTML arbitrario a trav\u00e9s de srcdoc, anulando por completo el sandboxing de rebote previsto de CryptPad y permitiendo la inyecci\u00f3n de enlaces u otro contenido interactivo dentro de documentos controlados por el usuario. La causa ra\u00edz reside en c\u00f3mo el saneador clasifica y aplica las restricciones de etiquetas: aunque define listas de etiquetas prohibidas y restringidas, \u003ciframe\u003e es tratado como \u0027restringido\u0027 en lugar de \u0027prohibido\u0027. La aplicaci\u00f3n luego inspecciona solo el atributo src, por lo que emparejar un src benigno de tipo blob: con un srcdoc malicioso resulta en una renderizaci\u00f3n sin restricciones. Este problema ha sido solucionado en la versi\u00f3n 2026.2.0."
    }
  ],
  "id": "CVE-2026-26028",
  "lastModified": "2026-07-23T12:10:00.110",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.1,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 2.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-26028",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-05-20T19:31:12.220425Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-05-20T20:16:36.760",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/cryptpad/cryptpad/releases/tag/2026.2.0"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/cryptpad/cryptpad/security/advisories/GHSA-g2g4-47gv-p72v"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        },
        {
          "lang": "en",
          "value": "CWE-116"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.