LibVNCServer UltraZip Encoding Heap Out-of-bounds Read

{
  "id": "c734e8fb23947649b4fda8cdfd13270f712e1211da66428cdd42cfee3230d665",
  "url": "https://osv.dev/vulnerability/CVE-2026-32853",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "LibVNCServer UltraZip Encoding Heap Out-of-bounds Read",
    "summary": "LibVNCServer versions 0.9.15 and prior (fixed in commit 009008e) contain a heap out-of-bounds read vulnerability in the UltraZip encoding handler that allows a malicious VNC server to cause information disclosure or application crash. Attackers can exploit improper bounds checking in the HandleUltraZipBPP() function by manipulating subrectangle header counts to read beyond the allocated heap buffer.",
    "evidence": "osv:CVE-2026-32853",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-32853",
      "aliases": [
        "CVE-2026-32853",
        "GHSA-87q7-v983-qwcj"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/libvnc/libvncserver",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "9b54b1ec32731bd23158ca014dc18014db4194c3"
                },
                {
                  "fixed": "009008e2f4d5a54dd71f422070df3af7b3dbc931"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:libvncserver_project:libvncserver:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "0.9.15"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "009008e2f4d5a54dd71f422070df3af7b3dbc931"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "LibVNCServer-0.9.14",
            "LibVNCServer-0.9.13",
            "LibVNCServer-0.9.12",
            "LibVNCServer-0.9.11",
            "LibVNCServer-0.9.10",
            "LibVNCServer-0.9.9",
            "LibVNCServer-0.9.8",
            "X11VNC_0_9_12",
            "X11VNC_0_9_11",
            "X11VNC_0_9_10",
            "X11VNC_0_9_9",
            "X11VNC_0_9_8",
            "X11VNC_0_9_7",
            "X11VNC_REL_0_9_6",
            "X11VNC_REL_0_9_5",
            "X11VNC_REL_0_9_4"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-32853.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:30.279513910Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/32xxx/CVE-2026-32853.json",
        "https://github.com/LibVNC/libvncserver/security/advisories/GHSA-87q7-v983-qwcj",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-32853",
        "https://www.vulncheck.com/advisories/libvncserver-ultrazip-encoding-heap-out-of-bounds-read",
        "https://github.com/LibVNC/libvncserver/commit/009008e2f4d5a54dd71f422070df3af7b3dbc931",
        "https://github.com/LibVNC/libvncserver"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-125"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/32xxx/CVE-2026-32853.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-32853",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 497051,
  "published_at": "2026-03-24T17:30:40.061+00:00"
}