{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "3.2.0"
                  },
                  {
                    "last_affected": "4.4.0"
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandardRange"
              }
            ]
          },
          "events": [
            {
              "introduced": "b2a6fe9684434117eb6a344fc2721e3c26d989bf"
            },
            {
              "last_affected": "89d49680b39218af2e5b700cd3f4fdc122600ac4"
            }
          ],
          "repo": "https://github.com/eclipse-langium/langium",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-297v-g8mm-qj4h"
  ],
  "database_specific": {
    "cna_assigner": "eclipse",
    "cwe_ids": [
      "CWE-407"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/124xxx/CVE-2026-124683.json"
  },
  "details": "Eclipse Langium versions 3.2.0 through 4.4.0 contain an inefficient algorithmic complexity issue (CWE-407) in the opt-in IndentationAwareTokenBuilder and IndentationAwareLexer. When producing DEDENT tokens, the token builder recomputes line numbers by re-scanning the entire preceding document text. A document whose indentation changes on most lines then takes quadratic time to tokenize. Because tokenization is synchronous, a crafted document of a few hundred kilobytes can block the Node.js event loop for tens of seconds. That causes a DoS for every user served by the same process. Languages built with the DefaultLexer and DefaultTokenBuilder are unaffected.",
  "id": "CVE-2026-124683",
  "modified": "2026-11-10T02:30:43.172047866Z",
  "published": "2026-11-09T16:02:50.370Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/124xxx/CVE-2026-124683.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/eclipse-langium/langium/security/advisories/GHSA-297v-g8mm-qj4h"
    },
    {
      "type": "WEB",
      "url": "https://gitlab.eclipse.org/security/cve-assignment/-/work_items/553"
    },
    {
      "type": "WEB",
      "url": "https://gitlab.eclipse.org/security/vulnerability-reports/-/work_items/1069"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-124683"
    }
  ],
  "schema_version": "1.9.2",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ]
}