{"id":"PYSEC-2026-1835","summary":"pypdf and PyPDF2 possible Infinite Loop when a comment isn't followed by a character","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\u003e=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```","aliases":["CVE-2023-36464","GHSA-4vvm-4w3v-6mr8","PYSEC-2026-3008"],"modified":"2026-07-13T16:42:55.319975462Z","published":"2026-07-07T11:45:19.595160Z","references":[{"type":"WEB","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":"WEB","url":"https://github.com/py-pdf/pypdf/pull/1828"},{"type":"WEB","url":"https://github.com/py-pdf/pypdf/pull/969"},{"type":"FIX","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"},{"type":"PACKAGE","url":"https://pypi.org/project/pypdf2"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-4vvm-4w3v-6mr8"}],"affected":[{"package":{"name":"pypdf2","ecosystem":"PyPI","purl":"pkg:pypi/pypdf2"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"2.2.0"},{"fixed":"3.9.0"}]}],"versions":["2.10.0","2.10.1","2.10.2","2.10.3","2.10.4","2.10.5","2.10.6","2.10.7","2.10.8","2.10.9","2.11.0","2.11.1","2.11.2","2.12.0","2.12.1","2.2.0","2.2.1","2.3.0","2.3.1","2.4.0","2.4.1","2.4.2","2.5.0","2.6.0","2.7.0","2.8.0","2.8.1","2.9.0","3.0.0","3.0.1"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/pypdf2/PYSEC-2026-1835.yaml"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}