CVE-2026-67422 (GCVE-0-2026-67422)

Vulnerability from cvelistv5 – Published: 2026-08-06 20:26 – Updated: 2026-08-07 17:00
VLAI
Title
pymdown-extensions: Exponential-backtracking ReDoS in caret, tilde, betterem, and magiclink inline processors
Summary
pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimiter characters in exponentially many ways, causing catastrophic backtracking. As a result, a single untrusted Markdown line under 50 bytes rendered with markdown.markdown() in each extension's default configuration drives the rendering thread into unbounded CPU usage that grows exponentially with input length, enabling an unauthenticated remote attacker who can submit Markdown to cause denial of service. The exposure is concrete for web applications that render user-supplied Markdown (comments, wikis, issue bodies, live preview), including any app using pymdownx.extra which bundles the vulnerable betterem default, as well as hosted docs/CI systems that build untrusted Markdown. The issue has been fixed in version 11.0.1.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: poc Automatable: yes Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-1333 - Inefficient Regular Expression Complexity
Assigner
References
Impacted products
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-67422",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-08-07T16:59:03.019688Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-08-07T17:00:29.808Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/facelessuser/pymdown-extensions/security/advisories/GHSA-gm37-52c6-37mw"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "pymdown-extensions",
          "vendor": "facelessuser",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 11.0.1"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimiter characters in exponentially many ways, causing catastrophic backtracking. As a result, a single untrusted Markdown line under 50 bytes rendered with markdown.markdown() in each extension\u0027s default configuration drives the rendering thread into unbounded CPU usage that grows exponentially with input length, enabling an unauthenticated remote attacker who can submit Markdown to cause denial of service. The exposure is concrete for web applications that render user-supplied Markdown (comments, wikis, issue bodies, live preview), including any app using pymdownx.extra which bundles the vulnerable betterem default, as well as hosted docs/CI systems that build untrusted Markdown. The issue has been fixed in version 11.0.1."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-1333",
              "description": "CWE-1333: Inefficient Regular Expression Complexity",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-06T20:26:31.930Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/facelessuser/pymdown-extensions/security/advisories/GHSA-gm37-52c6-37mw",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/facelessuser/pymdown-extensions/security/advisories/GHSA-gm37-52c6-37mw"
        },
        {
          "name": "https://github.com/facelessuser/pymdown-extensions/commit/c68498598d7b13011bb4571350b6e3612a4ce44b",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/facelessuser/pymdown-extensions/commit/c68498598d7b13011bb4571350b6e3612a4ce44b"
        }
      ],
      "source": {
        "advisory": "GHSA-gm37-52c6-37mw",
        "discovery": "UNKNOWN"
      },
      "title": "pymdown-extensions: Exponential-backtracking ReDoS in caret, tilde, betterem, and magiclink inline processors"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-67422",
    "datePublished": "2026-08-06T20:26:31.930Z",
    "dateReserved": "2026-07-29T15:02:20.413Z",
    "dateUpdated": "2026-08-07T17:00:29.808Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-67422",
      "date": "2026-08-08",
      "epss": "0.00582",
      "percentile": "0.44606"
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-08-07T18:01:03+00:00",
      "cve": "CVE-2026-67422",
      "id": "CVE-2026-67422",
      "initial_release_date": "2026-08-06T20:26:31.930000+00:00",
      "product_status:known_affected": "4",
      "product_status:known_not_affected": "2",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "pymdown-extensions: Pymdown-extensions: Denial of Service via Regular Expression Vulnerability",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-67422.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-67422\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"poc\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-08-07T16:59:03.019688Z\"}}}], \"references\": [{\"url\": \"https://github.com/facelessuser/pymdown-extensions/security/advisories/GHSA-gm37-52c6-37mw\", \"tags\": [\"exploit\"]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-08-07T17:00:23.457Z\"}}], \"cna\": {\"title\": \"pymdown-extensions: Exponential-backtracking ReDoS in caret, tilde, betterem, and magiclink inline processors\", \"source\": {\"advisory\": \"GHSA-gm37-52c6-37mw\", \"discovery\": \"UNKNOWN\"}, \"metrics\": [{\"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.5, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H\", \"integrityImpact\": \"NONE\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"NONE\"}}], \"affected\": [{\"vendor\": \"facelessuser\", \"product\": \"pymdown-extensions\", \"versions\": [{\"status\": \"affected\", \"version\": \"\u003c 11.0.1\"}]}], \"references\": [{\"url\": \"https://github.com/facelessuser/pymdown-extensions/security/advisories/GHSA-gm37-52c6-37mw\", \"name\": \"https://github.com/facelessuser/pymdown-extensions/security/advisories/GHSA-gm37-52c6-37mw\", \"tags\": [\"x_refsource_CONFIRM\"]}, {\"url\": \"https://github.com/facelessuser/pymdown-extensions/commit/c68498598d7b13011bb4571350b6e3612a4ce44b\", \"name\": \"https://github.com/facelessuser/pymdown-extensions/commit/c68498598d7b13011bb4571350b6e3612a4ce44b\", \"tags\": [\"x_refsource_MISC\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"pymdown-extensions is a collection of extensions for the Python Markdown library. In versions up to and including 11.0, four inline processors (caret, tilde, betterem, and magiclink) use regular expressions whose content groups can partition a run of delimiter characters in exponentially many ways, causing catastrophic backtracking. As a result, a single untrusted Markdown line under 50 bytes rendered with markdown.markdown() in each extension\u0027s default configuration drives the rendering thread into unbounded CPU usage that grows exponentially with input length, enabling an unauthenticated remote attacker who can submit Markdown to cause denial of service. The exposure is concrete for web applications that render user-supplied Markdown (comments, wikis, issue bodies, live preview), including any app using pymdownx.extra which bundles the vulnerable betterem default, as well as hosted docs/CI systems that build untrusted Markdown. The issue has been fixed in version 11.0.1.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-1333\", \"description\": \"CWE-1333: Inefficient Regular Expression Complexity\"}]}], \"providerMetadata\": {\"orgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"shortName\": \"GitHub_M\", \"dateUpdated\": \"2026-08-06T20:26:31.930Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-67422\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-07T17:00:29.808Z\", \"dateReserved\": \"2026-07-29T15:02:20.413Z\", \"assignerOrgId\": \"a0819718-46f1-4df5-94e2-005712e83aaa\", \"datePublished\": \"2026-08-06T20:26:31.930Z\", \"assignerShortName\": \"GitHub_M\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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.