{"id":"CVE-2023-36464","aliases":["GHSA-4vvm-4w3v-6mr8","PYSEC-2026-1835","PYSEC-2026-3008"],"title":"pypdf and PyPDF2 possible Infinite Loop when a comment isn't followed by a character","summary":"pypdf and PyPDF2 possible Infinite Loop when a comment isn't followed by a character","severity":"medium","cvss":6.2,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","vendor":"pypdf","product":"pypdf","ecosystem":"pip","affected":["pypdf >= 3.1.0, < 3.9.0","pypdf2 >= 2.2.0, <= 3.0.1"],"patched":["pypdf 3.9.0"],"published":"2023-06-30","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:50:01.918644849Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-4vvm-4w3v-6mr8","references":[{"url":"https://github.com/py-pdf/pypdf/security/advisories/GHSA-4vvm-4w3v-6mr8"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2023-36464"},{"url":"https://github.com/py-pdf/pypdf/pull/1828"},{"url":"https://github.com/py-pdf/pypdf/pull/969"},{"url":"https://github.com/py-pdf/pypdf/commit/b0e5c689df689ab173df84dacd77b6fc3c161932"},{"url":"https://github.com/py-pdf/pypdf"},{"url":"https://github.com/py-pdf/pypdf/releases/tag/3.9.0"}],"tags":["osv","pip"],"epss":0.00352,"epssPercentile":0.28982,"ingestedAt":"2026-07-08T18:25:45.692Z","slug":"CVE-2023-36464","body":"## Overview\n\n### 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```\n\n## Affected packages\n\n- `pypdf >= 3.1.0, < 3.9.0`\n- `pypdf2 >= 2.2.0, <= 3.0.1`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `pypdf 3.9.0`","depth":"sunlit","depthScore":34,"depthScoreParts":{"impact":34.1,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}