{
  "document": {
    "aggregate_severity": {
      "text": "Critical"
    },
    "category": "csaf_vex",
    "csaf_version": "2.0",
    "distribution": {
      "text": "TuxCare License Agreement",
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        "label": "WHITE",
        "url": "https://www.first.org/tlp/"
      }
    },
    "lang": "en",
    "notes": [
      {
        "category": "legal_disclaimer",
        "text": "This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Cloud Linux Inc. and provide a link to the original.",
        "title": "Terms of Use"
      }
    ],
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      "contact_details": "https://tuxcare.com/contact/",
      "name": "TuxCare",
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        "category": "self",
        "summary": "Canonical URL",
        "url": "https://security.tuxcare.com/csaf/v2/els_os/debian11els/vex/2026/cve-2026-27820-els_os-debian11els.json"
      }
    ],
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      "generator": {
        "date": "2026-10-15T17:59:15Z",
        "engine": {
          "name": "pyCSAF"
        }
      },
      "id": "CVE-2026-27820-ELS_OS-DEBIAN11ELS",
      "initial_release_date": "2026-04-16T18:16:00Z",
      "revision_history": [
        {
          "date": "2026-04-16T18:16:00Z",
          "number": "1",
          "summary": "Initial version"
        },
        {
          "date": "2026-10-09T00:34:27Z",
          "number": "2",
          "summary": "Official Publication"
        },
        {
          "date": "2026-10-15T17:59:15Z",
          "number": "3",
          "summary": "Update document"
        }
      ],
      "status": "final",
      "version": "3"
    },
    "title": "Security update on CVE-2026-27820"
  },
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  "vulnerabilities": [
    {
      "cve": "CVE-2026-27820",
      "cwe": {
        "id": "CWE-120",
        "name": "Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')"
      },
      "notes": [
        {
          "category": "description",
          "text": "zlib is a Ruby interface for the zlib compression/decompression library. Versions 3.0.0 and below, 3.1.0, 3.1.1, 3.2.0 and 3.2.1 contain a buffer overflow vulnerability in the Zlib::GzipReader. The zstream_buffer_ungets function prepends caller-provided bytes ahead of previously produced output but fails to guarantee the backing Ruby string has enough capacity before the memmove shifts the existing data. This can lead to memory corruption when the buffer length exceeds capacity. This issue has been fixed in versions 3.0.1, 3.1.2 and 3.2.3.",
          "title": "Vulnerability description"
        },
        {
          "category": "other",
          "text": "TuxCare has assessed that this vulnerability does not impact any currently supported TuxCare products. This evaluation may change as new information becomes available. For additional details regarding this vulnerability and affected products, refer to the provided references.",
          "title": "Statement"
        }
      ],
      "product_status": {
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          "Debian-11:zlib1g-dev-1:1.2.11.dfsg-2+deb11u2+tuxcare.els1.amd64",
          "Debian-11:zlib1g-dev-1:1.2.11.dfsg-2+deb11u2+tuxcare.els1.arm64",
          "Debian-11:zlib1g-dev-1:1.2.11.dfsg-2+deb11u2+tuxcare.els1.armel"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "Canonical URL",
          "url": "https://cve.tuxcare.com/els/cve/CVE-2026-27820"
        },
        {
          "category": "external",
          "summary": "https://github.com/ruby/zlib/security/advisories/GHSA-g857-hhfv-j68w",
          "url": "https://github.com/ruby/zlib/security/advisories/GHSA-g857-hhfv-j68w"
        },
        {
          "category": "external",
          "summary": "https://hackerone.com/reports/3467067",
          "url": "https://hackerone.com/reports/3467067"
        }
      ],
      "release_date": "2026-04-16T18:16:00Z",
      "threats": [
        {
          "category": "impact",
          "details": "Critical"
        },
        {
          "category": "impact",
          "date": "2026-10-15T15:26:43.299934Z",
          "details": "CVE-2026-27820 affects the Ruby zlib gem, the Ruby bindings for the zlib compression library, which are not part of the zlib package for Debian 11 ELS. The zlib package ships the C compression library (zlib1g and related binaries) and contains no Ruby bindings or the vulnerable zstream_buffer_ungets function.",
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            "Debian-11:zlib1g-1:1.2.11.dfsg-2+deb11u2+tuxcare.els1.arm64",
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            "Debian-11:zlib1g-dev-1:1.2.11.dfsg-2+deb11u2+tuxcare.els1.arm64",
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}