{
  "affected": [
    {
      "affectedData": [
        {
          "product": "libsixel",
          "vendor": "saitoha",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 1.8.7-r1"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:saitoha:libsixel:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "E16EAA6A-544F-4D16-829D-1B7C9979EA6A",
              "versionEndExcluding": "1.8.7-r1",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya\u0027s sixel. Versions 1.8.7 and prior contain a use-after-free vulnerability in sixel_encoder_encode_bytes() because sixel_frame_init() stores the caller-owned pixel buffer pointer directly in frame-\u003epixels without making a defensive copy. When a resize operation is triggered, sixel_frame_convert_to_rgb888() unconditionally frees this caller-owned buffer and replaces it with a new internal allocation, leaving the caller with a dangling pointer. Any subsequent access to the original buffer by the caller constitutes a use-after-free, confirmed by AddressSanitizer. An attacker who controls incoming frames can trigger this bug repeatedly and predictably, resulting in a reliable crash with potential for code execution. This issue has been fixed in version 1.8.7-r1."
    },
    {
      "lang": "es",
      "value": "libsixel es una implementaci\u00f3n de codificador/decodificador SIXEL derivada de sixel de kmiya. Las versiones 1.8.7 y anteriores contienen una vulnerabilidad de uso despu\u00e9s de liberaci\u00f3n en sixel_encoder_encode_bytes() porque sixel_frame_init() almacena el puntero del b\u00fafer de p\u00edxeles propiedad del llamador directamente en frame  -\u003e  pixels sin hacer una copia defensiva. Cuando se activa una operaci\u00f3n de redimensionamiento, sixel_frame_convert_to_rgb888() libera incondicionalmente este b\u00fafer propiedad del llamador y lo reemplaza con una nueva asignaci\u00f3n interna, dejando al llamador con un puntero colgante. Cualquier acceso posterior al b\u00fafer original por parte del llamador constituye un uso despu\u00e9s de liberaci\u00f3n, confirmado por AddressSanitizer. Un atacante que controla los fotogramas entrantes puede activar este error de forma repetida y predecible, lo que resulta en un fallo fiable con potencial para la ejecuci\u00f3n de c\u00f3digo. Este problema ha sido solucionado en la versi\u00f3n 1.8.7-r1."
    }
  ],
  "id": "CVE-2026-33021",
  "lastModified": "2026-07-25T11:10:00.100",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.3,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 2.5,
        "impactScore": 4.7,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-33021",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-04-16T13:54:16.495174Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-04-14T23:16:27.660",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Release Notes"
      ],
      "url": "https://github.com/saitoha/libsixel/releases/tag/v1.8.7-r1"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/saitoha/libsixel/security/advisories/GHSA-j6m5-2cc7-3whc"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-416"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}