Vulnerability-Lookup

PYSEC-2026-168

Vulnerability from pysec - Published: 2026-05-26 21:16 - Updated: 2026-05-29 10:50

Details

Mistune is a Python Markdown parser with renderers and plugins. In 3.2.0 and realier, in src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping. This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer.

Severity

6.1 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Impacted products

Name	purl
mistune	pkg:pypi/mistune

Aliases

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {},
      "package": {
        "ecosystem": "PyPI",
        "name": "mistune",
        "purl": "pkg:pypi/mistune"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.2.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.0",
        "0.2.0",
        "0.3.0",
        "0.3.1",
        "0.4",
        "0.4.1",
        "0.5",
        "0.5.1",
        "0.6",
        "0.7",
        "0.7.1",
        "0.7.2",
        "0.7.3",
        "0.7.4",
        "0.8",
        "0.8.1",
        "0.8.2",
        "0.8.3",
        "0.8.4",
        "2.0.0",
        "2.0.0a1",
        "2.0.0a2",
        "2.0.0a3",
        "2.0.0a4",
        "2.0.0a5",
        "2.0.0a6",
        "2.0.0rc1",
        "2.0.1",
        "2.0.2",
        "2.0.3",
        "2.0.4",
        "2.0.5",
        "3.0.0",
        "3.0.0a1",
        "3.0.0a2",
        "3.0.0a3",
        "3.0.0rc1",
        "3.0.0rc2",
        "3.0.0rc3",
        "3.0.0rc4",
        "3.0.0rc5",
        "3.0.1",
        "3.0.2",
        "3.1.0",
        "3.1.1",
        "3.1.2",
        "3.1.3",
        "3.1.4",
        "3.2.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44896",
    "GHSA-58cw-g322-p94v"
  ],
  "details": "Mistune is a Python Markdown parser with renderers and plugins. In 3.2.0 and realier, in src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping. This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer.",
  "id": "PYSEC-2026-168",
  "modified": "2026-05-29T10:50:12.284924Z",
  "published": "2026-05-26T21:16:39.477Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-58cw-g322-p94v"
    }
  ],
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-44896 (GCVE-0-2026-44896)

Vulnerability from cvelistv5 – Published: 2026-05-26 20:33 – Updated: 2026-05-27 13:19

Title

Mistune: XSS via unescaped figclass/figwidth in Figure directive

Summary

Severity

5.3 (Medium)


                        
                          CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Assigner

GitHub_M

References

1 reference

URL	Tags
https://github.com/lepture/mistune/security/advis…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version
lepture	mistune	Affected: <= 3.2.0

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-44896",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-27T13:06:28.976965Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-27T13:19:00.807Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "mistune",
          "vendor": "lepture",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c= 3.2.0"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Mistune is a Python Markdown parser with renderers and plugins. In 3.2.0 and realier, in src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping. This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "LOW",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "PASSIVE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "NONE"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-79",
              "description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-26T20:33:38.696Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/lepture/mistune/security/advisories/GHSA-58cw-g322-p94v",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/lepture/mistune/security/advisories/GHSA-58cw-g322-p94v"
        }
      ],
      "source": {
        "advisory": "GHSA-58cw-g322-p94v",
        "discovery": "UNKNOWN"
      },
      "title": "Mistune: XSS via unescaped figclass/figwidth in Figure directive"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-44896",
    "datePublished": "2026-05-26T20:33:38.696Z",
    "dateReserved": "2026-05-07T21:50:33.546Z",
    "dateUpdated": "2026-05-27T13:19:00.807Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

GHSA-58CW-G322-P94V

Vulnerability from github – Published: 2026-05-08 23:43 – Updated: 2026-05-08 23:43

Summary

Mistune has XSS via unescaped figclass/figwidth in Figure directive

Details

In src/mistune/directives/image.py, the render_figure() function concatenates figclass and figwidth options directly into HTML attributes without escaping (lines 152-168).

This allows attribute injection and XSS even when HTMLRenderer(escape=True) is used, because these values bypass the inline renderer.

Other attributes in the same file (src, alt, style) are properly escaped; figclass/figwidth were missed.

Severity

5.3 (Medium)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mistune"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "3.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-44896"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-08T23:43:12Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "In `src/mistune/directives/image.py`, the `render_figure()` function concatenates `figclass` and `figwidth` options directly into HTML attributes without escaping (lines 152-168).\n\nThis allows attribute injection and XSS even when `HTMLRenderer(escape=True)` is used, because these values bypass the inline renderer.\n\nOther attributes in the same file (src, alt, style) are properly escaped; figclass/figwidth were missed.",
  "id": "GHSA-58cw-g322-p94v",
  "modified": "2026-05-08T23:43:12Z",
  "published": "2026-05-08T23:43:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-58cw-g322-p94v"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Mistune has XSS via unescaped figclass/figwidth in Figure directive"
}

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.

Action not permitted

PYSEC-2026-168

CVE-2026-44896 (GCVE-0-2026-44896)

GHSA-58CW-G322-P94V

Tags

Sightings

Nomenclature