{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "1.3.1.2"
              },
              {
                "last_affected": "1.3.2"
              },
              {
                "fixed": "1.3.2"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "DESCRIPTION"
            ]
          },
          "events": [
            {
              "introduced": "570720b0c24f9686c33f35a1b3165c1f568b96be"
            },
            {
              "fixed": "da607da739fa6047df13e66a2af6b8bec7c2a498"
            }
          ],
          "repo": "https://github.com/madler/zlib",
          "type": "GIT"
        }
      ]
    }
  ],
  "database_specific": {
    "cna_assigner": "VulnCheck",
    "cwe_ids": [
      "CWE-787"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85091.json"
  },
  "details": "zlib versions 1.3.1.2 through 1.3.2 contain a heap buffer overflow vulnerability in the gz_vacate() function when processing non-blocking gzwrite() operations with stale external buffer pointers. Attackers can trigger the overflow by calling gzprintf() or gzvprintf() after a write stall, causing an unchecked memmove() to write beyond the internal input buffer boundary.",
  "id": "CVE-2026-85091",
  "modified": "2026-09-05T03:31:10.796209666Z",
  "published": "2026-09-03T01:04:44.460Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/85xxx/CVE-2026-85091.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-85091"
    },
    {
      "type": "ADVISORY",
      "url": "https://www.vulncheck.com/advisories/zlib-1.3.1.2-through-1.3.2-heap-buffer-overflow-via-gz-vacate"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/madler/zlib"
    },
    {
      "type": "ARTICLE",
      "url": "https://github.com/madler/zlib/blob/v1.3.2/gzwrite.c#L393"
    },
    {
      "type": "EVIDENCE",
      "url": "https://gist.github.com/thesmartshadow/e0b9481792afb7c31e86fee1ff084490"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "zlib 1.3.1.2 through 1.3.2 Heap Buffer Overflow via gz_vacate"
}