GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

USN-6483-1 (UBUNTU-CVE-2021-33391)

Vulnerability from osv_ubuntu – Published: 2023-11-15 14:31 – Updated: 2026-04-27 14:11 – Source website
VLAI
Summary
tidy-html5 vulnerability
Details

Neeraj Pal discovered that HTML Tidy incorrectly handled parsing certain HTML data. If a user or automated system were tricked into parsing specially crafted HTML data, a remote attacker could cause HTML Tidy to consume resources, leading to a denial of service, or possibly execute arbitrary code.

References
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "cves_map": {
          "cves": [
            {
              "id": "CVE-2021-33391",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                  "type": "CVSS_V3"
                },
                {
                  "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            }
          ],
          "ecosystem": "Ubuntu:20.04:LTS"
        }
      },
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libtidy5deb1",
            "binary_version": "2:5.6.0-11ubuntu0.20.04.1"
          },
          {
            "binary_name": "tidy",
            "binary_version": "2:5.6.0-11ubuntu0.20.04.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:20.04:LTS",
        "name": "tidy-html5",
        "purl": "pkg:deb/ubuntu/tidy-html5@2:5.6.0-11ubuntu0.20.04.1?arch=source\u0026distro=focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2:5.6.0-11ubuntu0.20.04.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2:5.6.0-10",
        "2:5.6.0-11"
      ]
    },
    {
      "database_specific": {
        "cves_map": {
          "cves": [
            {
              "id": "CVE-2021-33391",
              "severity": [
                {
                  "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                  "type": "CVSS_V3"
                },
                {
                  "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                  "type": "CVSS_V3"
                },
                {
                  "score": "medium",
                  "type": "Ubuntu"
                }
              ]
            }
          ],
          "ecosystem": "Ubuntu:22.04:LTS"
        }
      },
      "ecosystem_specific": {
        "availability": "No subscription required",
        "binaries": [
          {
            "binary_name": "libtidy5deb1",
            "binary_version": "2:5.6.0-11ubuntu0.22.04.1"
          },
          {
            "binary_name": "tidy",
            "binary_version": "2:5.6.0-11ubuntu0.22.04.1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:22.04:LTS",
        "name": "tidy-html5",
        "purl": "pkg:deb/ubuntu/tidy-html5@2:5.6.0-11ubuntu0.22.04.1?arch=source\u0026distro=jammy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2:5.6.0-11ubuntu0.22.04.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2:5.6.0-11build1",
        "2:5.6.0-11build2"
      ]
    }
  ],
  "aliases": [],
  "details": "Neeraj Pal discovered that HTML Tidy incorrectly handled parsing certain\nHTML data. If a user or automated system were tricked into parsing\nspecially crafted HTML data, a remote attacker could cause HTML Tidy to\nconsume resources, leading to a denial of service, or possibly execute\narbitrary code.\n",
  "id": "USN-6483-1",
  "modified": "2026-04-27T14:11:31Z",
  "published": "2023-11-15T14:31:49Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://ubuntu.com/security/notices/USN-6483-1"
    },
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2021-33391"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "summary": "tidy-html5 vulnerability",
  "upstream": [
    "UBUNTU-CVE-2021-33391"
  ]
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.