Skip to content
Heist/ feed
Back to feed
UnratedFix available

libxmltok vulnerabilities

Type: advisorySources: OSV

It was discovered that Expat, contained with the xmltok library did not correctly handle certain integer arithmetic. If a user or automated system were tricked into opening a specially crafted file, an attacker could possibly cause a denial of service. (CVE-2026-56404, CVE-2026-56405)

Products
libxmltok
Affected versions
1.2-3build3, 1.2-4, 1.2-4.1ubuntu1, 1.2-4.1ubuntu2, 1.2-4.1ubuntu2.24.0.4.1+esm1, 1.2-4.1ubuntu2.24.0.4.1+esm2, 1.2-4.1ubuntu2.24.0.4.1+esm3, 1.2-4.1ubuntu2.24.0.4.1+esm4, 1.2-4ubuntu0.18.04.1~esm1, 1.2-4ubuntu0.18.04.1~esm2, 1.2-4ubuntu0.18.04.1~esm3, 1.2-4ubuntu0.18.04.1~esm4, 1.2-4ubuntu0.18.04.1~esm5, 1.2-4ubuntu0.18.04.1~esm6, 1.2-4ubuntu0.20.04.1~esm1, 1.2-4ubuntu0.20.04.1~esm2, 1.2-4ubuntu0.20.04.1~esm3, 1.2-4ubuntu0.20.04.1~esm4, 1.2-4ubuntu0.20.04.1~esm5, 1.2-4ubuntu0.20.04.1~esm6, 1.2-4ubuntu0.22.04.1~esm1, 1.2-4ubuntu0.22.04.1~esm2, 1.2-4ubuntu0.22.04.1~esm3, 1.2-4ubuntu0.22.04.1~esm4, 1.2-4ubuntu0.22.04.1~esm5, 1.2-4ubuntu0.22.04.1~esm6, 1.2-4ubuntu1
Fixed versions
1.2-3ubuntu0.1~esm1, 1.2-4.1ubuntu2.24.0.4.1+esm5, 1.2-4ubuntu0.18.04.1~esm7, 1.2-4ubuntu0.20.04.1~esm7, 1.2-4ubuntu0.22.04.1~esm7
CVEs
CVE-2026-56404, CVE-2026-56405
Confirmed fixed CVEs
Not specified
Updated in this feed
27 Oct 2026, 10:43 UTC · Revision 1

Source evidence

libxmltok vulnerabilities

core-osv · Original source

Published 5 Oct 2026, 23:54 UTC

It was discovered that Expat, contained with the xmltok library did not correctly handle certain integer arithmetic. If a user or automated system were tricked into opening a specially crafted file, an attacker could possibly cause a denial of service. (CVE-2026-56404, CVE-2026-56405)

osv:USN-8872-1

libxmltok

Fixed versions: 1.2-3ubuntu0.1~esm1

libxmltok

Fixed versions: 1.2-4ubuntu0.18.04.1~esm7

libxmltok

Fixed versions: 1.2-4ubuntu0.20.04.1~esm7

libxmltok

Fixed versions: 1.2-4ubuntu0.22.04.1~esm7

libxmltok

Fixed versions: 1.2-4.1ubuntu2.24.0.4.1+esm5

Complete source record
{
  "id": "a2fcfa73cd35b4c963b55db284a472c709f1683dd8405a39b533a43f5bf71579",
  "url": "https://osv.dev/vulnerability/USN-8872-1",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "libxmltok vulnerabilities",
    "summary": "It was discovered that Expat, contained with the xmltok library did not correctly handle certain integer arithmetic. If a user or automated system were tricked into opening a specially crafted file, an attacker could possibly cause a denial of service. (CVE-2026-56404, CVE-2026-56405)",
    "evidence": "osv:USN-8872-1",
    "products": [
      {
        "name": {
          "value": "libxmltok",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.2-3ubuntu0.1~esm1",
            "evidence": "/affected/0/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "1.2-3build3",
            "evidence": "/affected/0/versions"
          }
        ]
      },
      {
        "name": {
          "value": "libxmltok",
          "evidence": "/affected/1/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.2-4ubuntu0.18.04.1~esm7",
            "evidence": "/affected/1/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "1.2-4",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "1.2-4ubuntu0.18.04.1~esm1",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "1.2-4ubuntu0.18.04.1~esm2",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "1.2-4ubuntu0.18.04.1~esm3",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "1.2-4ubuntu0.18.04.1~esm4",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "1.2-4ubuntu0.18.04.1~esm5",
            "evidence": "/affected/1/versions"
          },
          {
            "value": "1.2-4ubuntu0.18.04.1~esm6",
            "evidence": "/affected/1/versions"
          }
        ]
      },
      {
        "name": {
          "value": "libxmltok",
          "evidence": "/affected/2/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.2-4ubuntu0.20.04.1~esm7",
            "evidence": "/affected/2/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "1.2-4",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "1.2-4ubuntu0.20.04.1~esm1",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "1.2-4ubuntu0.20.04.1~esm2",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "1.2-4ubuntu0.20.04.1~esm3",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "1.2-4ubuntu0.20.04.1~esm4",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "1.2-4ubuntu0.20.04.1~esm5",
            "evidence": "/affected/2/versions"
          },
          {
            "value": "1.2-4ubuntu0.20.04.1~esm6",
            "evidence": "/affected/2/versions"
          }
        ]
      },
      {
        "name": {
          "value": "libxmltok",
          "evidence": "/affected/3/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.2-4ubuntu0.22.04.1~esm7",
            "evidence": "/affected/3/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "1.2-4",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "1.2-4ubuntu0.22.04.1~esm1",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "1.2-4ubuntu0.22.04.1~esm2",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "1.2-4ubuntu0.22.04.1~esm3",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "1.2-4ubuntu0.22.04.1~esm4",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "1.2-4ubuntu0.22.04.1~esm5",
            "evidence": "/affected/3/versions"
          },
          {
            "value": "1.2-4ubuntu0.22.04.1~esm6",
            "evidence": "/affected/3/versions"
          }
        ]
      },
      {
        "name": {
          "value": "libxmltok",
          "evidence": "/affected/4/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [
          {
            "value": "1.2-4.1ubuntu2.24.0.4.1+esm5",
            "evidence": "/affected/4/ranges"
          }
        ],
        "affected_versions": [
          {
            "value": "1.2-4ubuntu1",
            "evidence": "/affected/4/versions"
          },
          {
            "value": "1.2-4.1ubuntu1",
            "evidence": "/affected/4/versions"
          },
          {
            "value": "1.2-4.1ubuntu2",
            "evidence": "/affected/4/versions"
          },
          {
            "value": "1.2-4.1ubuntu2.24.0.4.1+esm1",
            "evidence": "/affected/4/versions"
          },
          {
            "value": "1.2-4.1ubuntu2.24.0.4.1+esm2",
            "evidence": "/affected/4/versions"
          },
          {
            "value": "1.2-4.1ubuntu2.24.0.4.1+esm3",
            "evidence": "/affected/4/versions"
          },
          {
            "value": "1.2-4.1ubuntu2.24.0.4.1+esm4",
            "evidence": "/affected/4/versions"
          }
        ]
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "USN-8872-1",
      "aliases": [
        "USN-8872-1"
      ],
      "affected": [
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1.2-3ubuntu0.1~esm1"
                }
              ]
            }
          ],
          "package": {
            "name": "libxmltok",
            "purl": "pkg:deb/ubuntu/libxmltok?arch=source&distro=esm-apps-legacy%2Fxenial",
            "ecosystem": "Ubuntu:Pro:16.04:LTS"
          },
          "versions": [
            "1.2-3build3"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8872-1.json",
            "cves_map": {
              "cves": [
                {
                  "id": "CVE-2026-56404",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                },
                {
                  "id": "CVE-2026-56405",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                }
              ],
              "ecosystem": "Ubuntu:Pro:16.04:LTS"
            }
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libxmltok1",
                "binary_version": "1.2-3ubuntu0.1~esm1"
              }
            ],
            "availability": "Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1.2-4ubuntu0.18.04.1~esm7"
                }
              ]
            }
          ],
          "package": {
            "name": "libxmltok",
            "purl": "pkg:deb/ubuntu/libxmltok?arch=source&distro=esm-apps%2Fbionic",
            "ecosystem": "Ubuntu:Pro:18.04:LTS"
          },
          "versions": [
            "1.2-4",
            "1.2-4ubuntu0.18.04.1~esm1",
            "1.2-4ubuntu0.18.04.1~esm2",
            "1.2-4ubuntu0.18.04.1~esm3",
            "1.2-4ubuntu0.18.04.1~esm4",
            "1.2-4ubuntu0.18.04.1~esm5",
            "1.2-4ubuntu0.18.04.1~esm6"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8872-1.json",
            "cves_map": {
              "cves": [
                {
                  "id": "CVE-2026-56404",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                },
                {
                  "id": "CVE-2026-56405",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                }
              ],
              "ecosystem": "Ubuntu:Pro:18.04:LTS"
            }
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libxmltok1",
                "binary_version": "1.2-4ubuntu0.18.04.1~esm7"
              }
            ],
            "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1.2-4ubuntu0.20.04.1~esm7"
                }
              ]
            }
          ],
          "package": {
            "name": "libxmltok",
            "purl": "pkg:deb/ubuntu/libxmltok?arch=source&distro=esm-apps%2Ffocal",
            "ecosystem": "Ubuntu:Pro:20.04:LTS"
          },
          "versions": [
            "1.2-4",
            "1.2-4ubuntu0.20.04.1~esm1",
            "1.2-4ubuntu0.20.04.1~esm2",
            "1.2-4ubuntu0.20.04.1~esm3",
            "1.2-4ubuntu0.20.04.1~esm4",
            "1.2-4ubuntu0.20.04.1~esm5",
            "1.2-4ubuntu0.20.04.1~esm6"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8872-1.json",
            "cves_map": {
              "cves": [
                {
                  "id": "CVE-2026-56404",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                },
                {
                  "id": "CVE-2026-56405",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                }
              ],
              "ecosystem": "Ubuntu:Pro:20.04:LTS"
            }
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libxmltok1",
                "binary_version": "1.2-4ubuntu0.20.04.1~esm7"
              }
            ],
            "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1.2-4ubuntu0.22.04.1~esm7"
                }
              ]
            }
          ],
          "package": {
            "name": "libxmltok",
            "purl": "pkg:deb/ubuntu/libxmltok?arch=source&distro=esm-apps%2Fjammy",
            "ecosystem": "Ubuntu:Pro:22.04:LTS"
          },
          "versions": [
            "1.2-4",
            "1.2-4ubuntu0.22.04.1~esm1",
            "1.2-4ubuntu0.22.04.1~esm2",
            "1.2-4ubuntu0.22.04.1~esm3",
            "1.2-4ubuntu0.22.04.1~esm4",
            "1.2-4ubuntu0.22.04.1~esm5",
            "1.2-4ubuntu0.22.04.1~esm6"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8872-1.json",
            "cves_map": {
              "cves": [
                {
                  "id": "CVE-2026-56404",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                },
                {
                  "id": "CVE-2026-56405",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                }
              ],
              "ecosystem": "Ubuntu:Pro:22.04:LTS"
            }
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libxmltok1",
                "binary_version": "1.2-4ubuntu0.22.04.1~esm7"
              }
            ],
            "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
          }
        },
        {
          "ranges": [
            {
              "type": "ECOSYSTEM",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "1.2-4.1ubuntu2.24.0.4.1+esm5"
                }
              ]
            }
          ],
          "package": {
            "name": "libxmltok",
            "purl": "pkg:deb/ubuntu/libxmltok?arch=source&distro=esm-apps%2Fnoble",
            "ecosystem": "Ubuntu:Pro:24.04:LTS"
          },
          "versions": [
            "1.2-4ubuntu1",
            "1.2-4.1ubuntu1",
            "1.2-4.1ubuntu2",
            "1.2-4.1ubuntu2.24.0.4.1+esm1",
            "1.2-4.1ubuntu2.24.0.4.1+esm2",
            "1.2-4.1ubuntu2.24.0.4.1+esm3",
            "1.2-4.1ubuntu2.24.0.4.1+esm4"
          ],
          "database_specific": {
            "source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8872-1.json",
            "cves_map": {
              "cves": [
                {
                  "id": "CVE-2026-56404",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                },
                {
                  "id": "CVE-2026-56405",
                  "severity": [
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "CVSS_V3",
                      "score": "CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L"
                    },
                    {
                      "type": "Ubuntu",
                      "score": "medium"
                    }
                  ]
                }
              ],
              "ecosystem": "Ubuntu:Pro:24.04:LTS"
            }
          },
          "ecosystem_specific": {
            "binaries": [
              {
                "binary_name": "libxmltok1t64",
                "binary_version": "1.2-4.1ubuntu2.24.0.4.1+esm5"
              }
            ],
            "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
          }
        }
      ],
      "modified": "2026-10-06T10:57:50.476314159Z",
      "provider": "osv",
      "upstream": [
        "CVE-2026-56404",
        "CVE-2026-56405",
        "UBUNTU-CVE-2026-56404",
        "UBUNTU-CVE-2026-56405"
      ],
      "references": [
        "https://ubuntu.com/security/notices/USN-8872-1",
        "https://ubuntu.com/security/CVE-2026-56404",
        "https://ubuntu.com/security/CVE-2026-56405"
      ]
    },
    "related_cves": [
      {
        "value": "CVE-2026-56404",
        "evidence": "/upstream"
      },
      {
        "value": "CVE-2026-56405",
        "evidence": "/upstream"
      }
    ],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 88881,
  "published_at": "2026-10-05T23:54:25+00:00"
}