{
  "cveId": "CVE-2026-33020",
  "url": "https://patchblox.com/security/cve/CVE-2026-33020",
  "summary": "CVE-2026-33020 is fixed in libsixel on 1 platform by DEBIAN-CVE-2026-33020 (version 1:1.8.7-r2-1), released April 14, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "libsixel: libsixel is a SIXEL encoder/decoder implementation derived from kmiya\u0027s sixel",
  "description": "libsixel is a SIXEL encoder/decoder implementation derived from kmiya\u0027s sixel. Versions 1.8.7 and prior contain an integer overflow which leads to a heap buffer overflow via sixel_frame_convert_to_rgb888() in frame.c, where allocation size and pointer offset computations for palettised images (PAL1, PAL2, PAL4) are performed using int arithmetic before casting to size_t. For images whose pixel count exceeds INT_MAX / 4, the overflow produces an undersized heap allocation for the conversion buffer and a negative pointer offset for the normalization sub-buffer, after which sixel_helper_normalize_pixelformat() writes the full image data starting from the invalid pointer, causing massive heap corruption confirmed by ASAN. An attacker providing a specially crafted large palettised PNG can corrupt the heap of the victim process, resulting in a reliable crash and potential arbitrary code execution. This issue has been fixed in version 1.8.7-r1.",
  "published": "2026-04-14T22:16:30Z",
  "severity": "high",
  "cvss": 7.1,
  "cvssVector": "CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H",
  "epss": 0.00205,
  "epssPercentile": 0.10532,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "libsixel",
      "release": "Debian 14",
      "fixedVersion": "1:1.8.7-r2-1",
      "fix": "DEBIAN-CVE-2026-33020",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-33020",
      "released": "2026-04-14T22:16:30Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T01:18:40Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}