FKIE_CVE-2026-33500

Vulnerability from fkie_nvd - Published: 2026-03-23 17:16 - Updated: 2026-06-17 10:37
Severity
5.4 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Summary
WWBN AVideo is an open source video platform. In versions up to and including 26.0, the fix for CVE-2026-27568 (GHSA-rcqw-6466-3mv7) introduced a custom `ParsedownSafeWithLinks` class that sanitizes raw HTML `<a>` and `<img>` tags in comments, but explicitly disables Parsedown's `safeMode`. This creates a bypass: markdown link syntax `[text](javascript:alert(1))` is processed by Parsedown's `inlineLink()` method, which does not go through the custom `sanitizeATag()` sanitization (that only handles raw HTML tags). With `safeMode` disabled, Parsedown's built-in `javascript:` URI filtering (`sanitiseElement()`/`filterUnsafeUrlInAttribute()`) is also inactive. An attacker can inject stored XSS via comment markdown links. Commit 3ae02fa240939dbefc5949d64f05790fd25d728d contains a patch.
References
security-advisories@github.comhttps://github.com/WWBN/AVideo/commit/3ae02fa240939dbefc5949d64f05790fd25d728dPatch
security-advisories@github.comhttps://github.com/WWBN/AVideo/security/advisories/GHSA-72h5-39r7-r26jExploit, Mitigation, Vendor Advisory
Impacted products
Vendor Product Version
wwbn avideo *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "AVideo",
          "vendor": "WWBN",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c= 26.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:wwbn:avideo:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "774C24F1-9D26-484F-B931-1DA107C8F588",
              "versionEndIncluding": "26.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "WWBN AVideo is an open source video platform. In versions up to and including 26.0, the fix for CVE-2026-27568 (GHSA-rcqw-6466-3mv7) introduced a custom `ParsedownSafeWithLinks` class that sanitizes raw HTML `\u003ca\u003e` and `\u003cimg\u003e` tags in comments, but explicitly disables Parsedown\u0027s `safeMode`. This creates a bypass: markdown link syntax `[text](javascript:alert(1))` is processed by Parsedown\u0027s `inlineLink()` method, which does not go through the custom `sanitizeATag()` sanitization (that only handles raw HTML tags). With `safeMode` disabled, Parsedown\u0027s built-in `javascript:` URI filtering (`sanitiseElement()`/`filterUnsafeUrlInAttribute()`) is also inactive. An attacker can inject stored XSS via comment markdown links. Commit 3ae02fa240939dbefc5949d64f05790fd25d728d contains a patch."
    },
    {
      "lang": "es",
      "value": "WWBN AVideo es una plataforma de video de c\u00f3digo abierto. En versiones hasta la 26.0 inclusive, la correcci\u00f3n para CVE-2026-27568 (GHSA-rcqw-6466-3mv7) introdujo una clase personalizada ParsedownSafeWithLinks que sanitiza las etiquetas HTML sin procesar `\u003ca rel=\"nofollow\"\u003e` e `` en los comentarios, pero deshabilita expl\u00edcitamente el safeMode de Parsedown. Esto crea un bypass: la sintaxis de enlace markdown `[text](javascript:alert(1))` es procesada por el m\u00e9todo inlineLink() de Parsedown, que no pasa por la sanitizaci\u00f3n personalizada sanitizeATag() (que solo maneja etiquetas HTML sin procesar). Con safeMode deshabilitado, el filtrado de URI `javascript:` incorporado de Parsedown (sanitiseElement()/filterUnsafeUrlInAttribute()) tambi\u00e9n est\u00e1 inactivo. Un atacante puede inyectar XSS almacenado a trav\u00e9s de enlaces markdown en comentarios. El commit 3ae02fa240939dbefc5949d64f05790fd25d728d contiene un parche.\u003c/a\u003e"
    }
  ],
  "id": "CVE-2026-33500",
  "lastModified": "2026-06-17T10:37:36.503",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.4,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "LOW",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.3,
        "impactScore": 2.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-33500",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-03-24T17:38:19.380717Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-03-23T17:16:51.340",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/WWBN/AVideo/commit/3ae02fa240939dbefc5949d64f05790fd25d728d"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Mitigation",
        "Vendor Advisory"
      ],
      "url": "https://github.com/WWBN/AVideo/security/advisories/GHSA-72h5-39r7-r26j"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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