{
  "document": {
    "aggregate_severity": {
      "text": "High"
    },
    "category": "csaf_vex",
    "csaf_version": "2.0",
    "distribution": {
      "text": "TuxCare License Agreement",
      "tlp": {
        "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"
      }
    ],
    "publisher": {
      "category": "vendor",
      "contact_details": "https://tuxcare.com/contact/",
      "name": "TuxCare",
      "namespace": "https://tuxcare.com/"
    },
    "references": [
      {
        "category": "self",
        "summary": "Canonical URL",
        "url": "https://security.tuxcare.com/csaf/v2/els_os/ubuntu20.04els/vex/2026/cve-2026-33636-els_os-ubuntu20_04els.json"
      }
    ],
    "tracking": {
      "current_release_date": "2026-08-05T13:42:43Z",
      "generator": {
        "date": "2026-08-05T13:42:43Z",
        "engine": {
          "name": "pyCSAF"
        }
      },
      "id": "CVE-2026-33636-ELS_OS-UBUNTU20.04ELS",
      "initial_release_date": "2026-03-26T17:16:00Z",
      "revision_history": [
        {
          "date": "2026-03-26T17:16:00Z",
          "number": "1",
          "summary": "Initial version"
        },
        {
          "date": "2026-08-02T07:14:07Z",
          "number": "2",
          "summary": "Official Publication"
        },
        {
          "date": "2026-08-05T13:42:43Z",
          "number": "3",
          "summary": "Update document"
        }
      ],
      "status": "final",
      "version": "3"
    },
    "title": "Security update on CVE-2026-33636"
  },
  "product_tree": {
    "branches": [
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_name",
                "name": "Ubuntu 20.04",
                "product": {
                  "name": "Ubuntu 20.04",
                  "product_id": "Ubuntu-20",
                  "product_identification_helper": {
                    "cpe": "cpe:2.3:o:canonical:ubuntu_linux:20.04:*:*:*:lts:*:*:*"
                  }
                }
              }
            ],
            "category": "product_family",
            "name": "Ubuntu"
          },
          {
            "branches": [
              {
                "category": "product_version",
                "name": "libpng-dev-0:1.6.37-2.amd64",
                "product": {
                  "name": "libpng-dev-0:1.6.37-2.amd64",
                  "product_id": "libpng-dev-0:1.6.37-2.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/ubuntu/libpng-dev@1.6.37-2?arch=amd64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "libpng-tools-0:1.6.37-2.amd64",
                "product": {
                  "name": "libpng-tools-0:1.6.37-2.amd64",
                  "product_id": "libpng-tools-0:1.6.37-2.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/ubuntu/libpng-tools@1.6.37-2?arch=amd64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "libpng16-16-0:1.6.37-2.amd64",
                "product": {
                  "name": "libpng16-16-0:1.6.37-2.amd64",
                  "product_id": "libpng16-16-0:1.6.37-2.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/ubuntu/libpng16-16@1.6.37-2?arch=amd64"
                  }
                }
              }
            ],
            "category": "architecture",
            "name": "amd64"
          }
        ],
        "category": "vendor",
        "name": "Canonical Ltd."
      },
      {
        "branches": [
          {
            "branches": [
              {
                "category": "product_version",
                "name": "libpng16-16-0:1.6.37-2+tuxcare.els2.amd64",
                "product": {
                  "name": "libpng16-16-0:1.6.37-2+tuxcare.els2.amd64",
                  "product_id": "libpng16-16-0:1.6.37-2+tuxcare.els2.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/tuxcare/libpng16-16@1.6.37-2%2Btuxcare.els2?arch=amd64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "libpng-dev-0:1.6.37-2+tuxcare.els2.amd64",
                "product": {
                  "name": "libpng-dev-0:1.6.37-2+tuxcare.els2.amd64",
                  "product_id": "libpng-dev-0:1.6.37-2+tuxcare.els2.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/tuxcare/libpng-dev@1.6.37-2%2Btuxcare.els2?arch=amd64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "libpng-tools-0:1.6.37-2+tuxcare.els2.amd64",
                "product": {
                  "name": "libpng-tools-0:1.6.37-2+tuxcare.els2.amd64",
                  "product_id": "libpng-tools-0:1.6.37-2+tuxcare.els2.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/tuxcare/libpng-tools@1.6.37-2%2Btuxcare.els2?arch=amd64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "libpng-dev-0:1.6.37-2+tuxcare.els4.amd64",
                "product": {
                  "name": "libpng-dev-0:1.6.37-2+tuxcare.els4.amd64",
                  "product_id": "libpng-dev-0:1.6.37-2+tuxcare.els4.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/tuxcare/libpng-dev@1.6.37-2%2Btuxcare.els4?arch=amd64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "libpng-tools-0:1.6.37-2+tuxcare.els4.amd64",
                "product": {
                  "name": "libpng-tools-0:1.6.37-2+tuxcare.els4.amd64",
                  "product_id": "libpng-tools-0:1.6.37-2+tuxcare.els4.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/tuxcare/libpng-tools@1.6.37-2%2Btuxcare.els4?arch=amd64"
                  }
                }
              },
              {
                "category": "product_version",
                "name": "libpng16-16-0:1.6.37-2+tuxcare.els4.amd64",
                "product": {
                  "name": "libpng16-16-0:1.6.37-2+tuxcare.els4.amd64",
                  "product_id": "libpng16-16-0:1.6.37-2+tuxcare.els4.amd64",
                  "product_identification_helper": {
                    "purl": "pkg:deb/tuxcare/libpng16-16@1.6.37-2%2Btuxcare.els4?arch=amd64"
                  }
                }
              }
            ],
            "category": "architecture",
            "name": "amd64"
          }
        ],
        "category": "vendor",
        "name": "TuxCare"
      }
    ],
    "relationships": [
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng16-16-0:1.6.37-2+tuxcare.els2.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng16-16-0:1.6.37-2+tuxcare.els2.amd64"
        },
        "product_reference": "libpng16-16-0:1.6.37-2+tuxcare.els2.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng-dev-0:1.6.37-2+tuxcare.els2.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng-dev-0:1.6.37-2+tuxcare.els2.amd64"
        },
        "product_reference": "libpng-dev-0:1.6.37-2+tuxcare.els2.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng-tools-0:1.6.37-2+tuxcare.els2.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng-tools-0:1.6.37-2+tuxcare.els2.amd64"
        },
        "product_reference": "libpng-tools-0:1.6.37-2+tuxcare.els2.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng-dev-0:1.6.37-2+tuxcare.els4.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng-dev-0:1.6.37-2+tuxcare.els4.amd64"
        },
        "product_reference": "libpng-dev-0:1.6.37-2+tuxcare.els4.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng-tools-0:1.6.37-2+tuxcare.els4.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng-tools-0:1.6.37-2+tuxcare.els4.amd64"
        },
        "product_reference": "libpng-tools-0:1.6.37-2+tuxcare.els4.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng16-16-0:1.6.37-2+tuxcare.els4.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng16-16-0:1.6.37-2+tuxcare.els4.amd64"
        },
        "product_reference": "libpng16-16-0:1.6.37-2+tuxcare.els4.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng-dev-0:1.6.37-2.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng-dev-0:1.6.37-2.amd64"
        },
        "product_reference": "libpng-dev-0:1.6.37-2.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng-tools-0:1.6.37-2.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng-tools-0:1.6.37-2.amd64"
        },
        "product_reference": "libpng-tools-0:1.6.37-2.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      },
      {
        "category": "default_component_of",
        "full_product_name": {
          "name": "libpng16-16-0:1.6.37-2.amd64 as a component of Ubuntu 20.04",
          "product_id": "Ubuntu-20:libpng16-16-0:1.6.37-2.amd64"
        },
        "product_reference": "libpng16-16-0:1.6.37-2.amd64",
        "relates_to_product_reference": "Ubuntu-20"
      }
    ]
  },
  "vulnerabilities": [
    {
      "cve": "CVE-2026-33636",
      "cwe": {
        "id": "CWE-125",
        "name": "Out-of-bounds Read"
      },
      "notes": [
        {
          "category": "description",
          "text": "LIBPNG is a reference library for use in applications that read, create, and manipulate PNG (Portable Network Graphics) raster image files. In versions 1.6.36 through 1.6.55, an out-of-bounds read and write exists in libpng's ARM/AArch64 Neon-optimized palette expansion path. When expanding 8-bit paletted rows to RGB or RGBA, the Neon loop processes a final partial chunk without verifying that enough input pixels remain. Because the implementation works backward from the end of the row, the final iteration dereferences pointers before the start of the row buffer (OOB read) and writes expanded pixel data to the same underflowed positions (OOB write). This is reachable via normal decoding of attacker-controlled PNG input if Neon is enabled. Version 1.6.56 fixes the issue.",
          "title": "Vulnerability description"
        },
        {
          "category": "general",
          "text": "The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.",
          "title": "CVSS score applicability"
        }
      ],
      "product_status": {
        "fixed": [
          "Ubuntu-20:libpng-dev-0:1.6.37-2+tuxcare.els4.amd64",
          "Ubuntu-20:libpng-tools-0:1.6.37-2+tuxcare.els4.amd64",
          "Ubuntu-20:libpng16-16-0:1.6.37-2+tuxcare.els4.amd64"
        ],
        "known_affected": [
          "Ubuntu-20:libpng-dev-0:1.6.37-2+tuxcare.els2.amd64",
          "Ubuntu-20:libpng-dev-0:1.6.37-2.amd64",
          "Ubuntu-20:libpng-tools-0:1.6.37-2+tuxcare.els2.amd64",
          "Ubuntu-20:libpng-tools-0:1.6.37-2.amd64",
          "Ubuntu-20:libpng16-16-0:1.6.37-2+tuxcare.els2.amd64",
          "Ubuntu-20:libpng16-16-0:1.6.37-2.amd64"
        ]
      },
      "references": [
        {
          "category": "self",
          "summary": "Canonical URL",
          "url": "https://cve.tuxcare.com/els/cve/CVE-2026-33636"
        },
        {
          "category": "external",
          "summary": "https://github.com/pnggroup/libpng/commit/7734cda20cf1236aef60f3bbd2267c97bbb40869",
          "url": "https://github.com/pnggroup/libpng/commit/7734cda20cf1236aef60f3bbd2267c97bbb40869"
        },
        {
          "category": "external",
          "summary": "https://github.com/pnggroup/libpng/commit/aba9f18eba870d14fb52c5ba5d73451349e339c3",
          "url": "https://github.com/pnggroup/libpng/commit/aba9f18eba870d14fb52c5ba5d73451349e339c3"
        },
        {
          "category": "external",
          "summary": "https://github.com/pnggroup/libpng/security/advisories/GHSA-wjr5-c57x-95m2",
          "url": "https://github.com/pnggroup/libpng/security/advisories/GHSA-wjr5-c57x-95m2"
        }
      ],
      "release_date": "2026-03-26T17:16:00Z",
      "remediations": [
        {
          "category": "none_available",
          "date": "2026-08-01T16:06:17.207091Z",
          "details": "Affected",
          "product_ids": [
            "Ubuntu-20:libpng-dev-0:1.6.37-2+tuxcare.els2.amd64",
            "Ubuntu-20:libpng-dev-0:1.6.37-2.amd64",
            "Ubuntu-20:libpng-tools-0:1.6.37-2+tuxcare.els2.amd64",
            "Ubuntu-20:libpng-tools-0:1.6.37-2.amd64",
            "Ubuntu-20:libpng16-16-0:1.6.37-2+tuxcare.els2.amd64",
            "Ubuntu-20:libpng16-16-0:1.6.37-2.amd64"
          ]
        },
        {
          "category": "vendor_fix",
          "date": "2026-08-05T13:42:01.751226Z",
          "details": "Details on how to apply the fix are available at: https://cve.tuxcare.com/els/releases/CLSA-2026:1785937319",
          "product_ids": [
            "Ubuntu-20:libpng-dev-0:1.6.37-2+tuxcare.els4.amd64",
            "Ubuntu-20:libpng-tools-0:1.6.37-2+tuxcare.els4.amd64",
            "Ubuntu-20:libpng16-16-0:1.6.37-2+tuxcare.els4.amd64"
          ],
          "url": "https://cve.tuxcare.com/els/releases/CLSA-2026:1785937319"
        }
      ],
      "scores": [
        {
          "cvss_v3": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.6,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:H",
            "version": "3.1"
          },
          "products": [
            "Ubuntu-20:libpng-dev-0:1.6.37-2+tuxcare.els2.amd64",
            "Ubuntu-20:libpng-dev-0:1.6.37-2+tuxcare.els4.amd64",
            "Ubuntu-20:libpng-dev-0:1.6.37-2.amd64",
            "Ubuntu-20:libpng-tools-0:1.6.37-2+tuxcare.els2.amd64",
            "Ubuntu-20:libpng-tools-0:1.6.37-2+tuxcare.els4.amd64",
            "Ubuntu-20:libpng-tools-0:1.6.37-2.amd64",
            "Ubuntu-20:libpng16-16-0:1.6.37-2+tuxcare.els2.amd64",
            "Ubuntu-20:libpng16-16-0:1.6.37-2+tuxcare.els4.amd64",
            "Ubuntu-20:libpng16-16-0:1.6.37-2.amd64"
          ]
        }
      ],
      "threats": [
        {
          "category": "impact",
          "details": "Important"
        }
      ]
    }
  ]
}