CVE-2026-33347 (GCVE-0-2026-33347)

Vulnerability from cvelistv5 – Published: 2026-03-24 19:26 – Updated: 2026-03-24 19:26
VLAI?
Title
league/commonmark has an embed extension allowed_domains bypass
Summary
league/commonmark is a PHP Markdown parser. From version 2.3.0 to before version 2.8.2, the DomainFilteringAdapter in the Embed extension is vulnerable to an allowlist bypass due to a missing hostname boundary assertion in the domain-matching regex. An attacker-controlled domain like youtube.com.evil passes the allowlist check when youtube.com is an allowed domain. This issue has been patched in version 2.8.2.
Severity ?
6.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N
CWE
  • CWE-79 - Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
  • CWE-185 - Incorrect Regular Expression
  • CWE-918 - Server-Side Request Forgery (SSRF)
Assigner
References
Impacted products
Vendor Product Version
thephpleague commonmark Affected: >= 2.3.0, < 2.8.2
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      "affected": [
        {
          "product": "commonmark",
          "vendor": "thephpleague",
          "versions": [
            {
              "status": "affected",
              "version": "\u003e= 2.3.0, \u003c 2.8.2"
            }
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        }
      ],
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        }
      ],
      "metrics": [
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            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "baseScore": 6.3,
            "baseSeverity": "MEDIUM",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "LOW",
            "subIntegrityImpact": "LOW",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "NONE",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "LOW"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-79",
              "description": "CWE-79: Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-185",
              "description": "CWE-185: Incorrect Regular Expression",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-918",
              "description": "CWE-918: Server-Side Request Forgery (SSRF)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-03-24T19:26:23.872Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/thephpleague/commonmark/security/advisories/GHSA-hh8v-hgvp-g3f5",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/thephpleague/commonmark/security/advisories/GHSA-hh8v-hgvp-g3f5"
        },
        {
          "name": "https://github.com/thephpleague/commonmark/commit/59fb075d2101740c337c7216e3f32b36c204218b",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/thephpleague/commonmark/commit/59fb075d2101740c337c7216e3f32b36c204218b"
        },
        {
          "name": "https://github.com/thephpleague/commonmark/releases/tag/2.8.2",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/thephpleague/commonmark/releases/tag/2.8.2"
        }
      ],
      "source": {
        "advisory": "GHSA-hh8v-hgvp-g3f5",
        "discovery": "UNKNOWN"
      },
      "title": "league/commonmark has an embed extension allowed_domains bypass"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-33347",
    "datePublished": "2026-03-24T19:26:23.872Z",
    "dateReserved": "2026-03-18T22:15:11.814Z",
    "dateUpdated": "2026-03-24T19:26:23.872Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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  }
}


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  • 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.
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  • 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.