{"id":"CVE-2023-36464","aliases":["GHSA-4vvm-4w3v-6mr8","PYSEC-2026-1835","PYSEC-2026-3008"],"url":"https://o3.security/vulnerability/CVE-2023-36464","summary":"Infinite Loop when a comment isn't followed by a character in pypdf","details":"### Impact\nAn attacker who uses this vulnerability can craft a PDF which leads to an infinite loop if `__parse_content_stream` is executed. This infinite loop blocks the current process and can utilize a single core of the CPU by 100%. It does not affect memory usage. That is, for example, the case if the user extracted text from such a PDF.\n\nExample Code and a PDF that causes the issue:\n\n```python\nfrom pypdf import PdfReader\n\n# https://objects.githubusercontent.com/github-production-repository-file-5c1aeb/3119517/11367871?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWNJYAX4CSVEH53A%2F20230627%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20230627T201018Z&X-Amz-Expires=300&X-Amz-Signature=d71c8fd9181c4875f0c04d563b6d32f1d4da6e7b2e6be2f14479ce4ecdc9c8b2&X-Amz-SignedHeaders=host&actor_id=1658117&key_id=0&repo_id=3119517&response-content-disposition=attachment%3Bfilename%3DMiFO_LFO_FEIS_NOA_Published.3.pdf&response-content-type=application%2Fpdf\nreader = PdfReader(\"MiFO_LFO_FEIS_NOA_Published.3.pdf\")\npage = reader.pages[0]\npage.extract_text()\n```\n\nThe issue was introduced with https://github.com/py-pdf/pypdf/pull/969\n\n### Patches\n\nThe issue was fixed with https://github.com/py-pdf/pypdf/pull/1828\n\n### Workarounds\n\nIt is recommended to upgrade to `pypdf>=3.9.0`. PyPDF2 users should migrate to pypdf.\n\nIf you cannot update your version of pypdf, you should modify `pypdf/generic/_data_structures.py`:\n\n```\nOLD: while peek not in (b\"\\r\", b\"\\n\"):\nNEW: while peek not in (b\"\\r\", b\"\\n\", b\"\"):\n```","published":"2023-06-27T21:24:30.685Z","modified":"2026-08-12T03:51:19.403560220Z","cvss":{"score":6.2,"severity":"MEDIUM","vector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":1,"affectedPackages":[{"ecosystem":"PyPI","name":"pypdf","fixedVersion":"3.9.0"},{"ecosystem":"PyPI","name":"pypdf2","fixedVersion":null}],"fix":{"url":"https://github.com/py-pdf/pypdf/pull/1828","label":"py-pdf/pypdf#1828"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2023/36xxx/CVE-2023-36464.json"},{"type":"ADVISORY","url":"https://github.com/py-pdf/pypdf/security/advisories/GHSA-4vvm-4w3v-6mr8"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-36464"},{"type":"FIX","url":"https://github.com/py-pdf/pypdf/pull/1828"},{"type":"FIX","url":"https://github.com/py-pdf/pypdf/pull/969"},{"type":"WEB","url":"https://github.com/py-pdf/pypdf/commit/b0e5c689df689ab173df84dacd77b6fc3c161932"},{"type":"PACKAGE","url":"https://github.com/py-pdf/pypdf"},{"type":"WEB","url":"https://github.com/py-pdf/pypdf/releases/tag/3.9.0"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:19.403560220Z"}}