pypdf: Possible infinite loop when processing threads/articles in writer

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-54651",
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "dateUpdated": "2026-06-22T20:28:28.412Z",
    "dateReserved": "2026-06-15T20:16:46.198Z",
    "datePublished": "2026-06-22T20:28:28.412Z",
    "state": "PUBLISHED"
  },
  "containers": {
    "cna": {
      "providerMetadata": {
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M",
        "dateUpdated": "2026-06-22T20:28:28.412Z"
      },
      "title": "pypdf: Possible infinite loop when processing threads/articles in writer",
      "descriptions": [
        {
          "lang": "en",
          "value": "pypdf is a free and open-source pure-python PDF library. Prior to 6.13.1, an attacker who uses this vulnerability can craft a PDF which leads to an infinite loop. This requires merging a file with threads/articles into a writer. This vulnerability is fixed in 6.13.1."
        }
      ],
      "affected": [
        {
          "vendor": "py-pdf",
          "product": "pypdf",
          "versions": [
            {
              "version": "< 6.13.1",
              "status": "affected"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop')",
              "cweId": "CWE-835",
              "type": "CWE"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://github.com/py-pdf/pypdf/security/advisories/GHSA-g9xf-7f8q-9mcj",
          "name": "https://github.com/py-pdf/pypdf/security/advisories/GHSA-g9xf-7f8q-9mcj",
          "tags": [
            "x_refsource_CONFIRM"
          ]
        },
        {
          "url": "https://github.com/py-pdf/pypdf/pull/3839",
          "name": "https://github.com/py-pdf/pypdf/pull/3839",
          "tags": [
            "x_refsource_MISC"
          ]
        },
        {
          "url": "https://github.com/py-pdf/pypdf/releases/tag/6.13.1",
          "name": "https://github.com/py-pdf/pypdf/releases/tag/6.13.1",
          "tags": [
            "x_refsource_MISC"
          ]
        }
      ],
      "metrics": [
        {}
      ]
    }
  }
}