Mistune 3.2.1 before 3.3.0 CSS Injection via Figure Directive figwidth Option

{
  "id": "aacff61cbbc7967a760ea98f23dd9ac5a7d97dba17f14af3519581bc6cd2a9fe",
  "url": "https://osv.dev/vulnerability/CVE-2026-115351",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Mistune 3.2.1 before 3.3.0 CSS Injection via Figure Directive figwidth Option",
    "summary": "Mistune from 3.2.1 before 3.3.0 contains a CSS injection vulnerability that allows attackers controlling markdown input to inject arbitrary style declarations via the unvalidated figwidth option of the figure directive. Attackers can append declarations like background:url() to the rendered figure style attribute, forcing victim browsers to send requests to attacker servers and leak attribute values.",
    "evidence": "osv:CVE-2026-115351",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-115351",
      "aliases": [
        "CVE-2026-115351",
        "GHSA-xmwc-wjpr-q378"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/lepture/mistune",
              "type": "GIT",
              "events": [
                {
                  "introduced": "067f90861088a496942f5eb43236135352b85d39"
                },
                {
                  "fixed": "15c3b79325125272263d7d42492ec8f757447191"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "3.2.1"
                      },
                      {
                        "fixed": "3.3.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "range": [
                      {
                        "introduced": "3.2.1"
                      },
                      {
                        "fixed": "3.3.0"
                      }
                    ],
                    "source": "DESCRIPTION"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v3.2.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-115351.json"
          }
        }
      ],
      "modified": "2026-10-31T02:30:22.826580600Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/115xxx/CVE-2026-115351.json",
        "https://github.com/lepture/mistune/security/advisories/GHSA-xmwc-wjpr-q378",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-115351",
        "https://www.vulncheck.com/advisories/mistune-3.2.1-before-3.3.0-css-injection-via-figure-directive-figwidth-option"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-94"
        ],
        "cna_assigner": "VulnCheck",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/115xxx/CVE-2026-115351.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-115351",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 508769,
  "published_at": "2026-10-22T19:13:27.678+00:00"
}