{"id":"CVE-2026-27026","aliases":["GHSA-9mvc-8737-8j8h","PYSEC-2026-3015"],"title":"pypdf possibly has long runtimes for malformed FlateDecode streams","summary":"pypdf possibly has long runtimes for malformed FlateDecode streams","severity":"medium","vendor":"pypdf","product":"pypdf","ecosystem":"pip","affected":["pypdf < 6.7.1"],"patched":["pypdf 6.7.1"],"published":"2026-02-18","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:50:34.680998937Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-9mvc-8737-8j8h","references":[{"url":"https://github.com/py-pdf/pypdf/security/advisories/GHSA-9mvc-8737-8j8h"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-27026"},{"url":"https://github.com/py-pdf/pypdf/pull/3644"},{"url":"https://github.com/py-pdf/pypdf/commit/7905842d833f899f1d3228af7e7467ad80277016"},{"url":"https://github.com/py-pdf/pypdf"},{"url":"https://github.com/py-pdf/pypdf/releases/tag/6.7.1"}],"tags":["osv","pip"],"epss":0.00184,"epssPercentile":0.07056,"ingestedAt":"2026-07-13T18:57:56.017Z","slug":"CVE-2026-27026","body":"## Overview\n\n### Impact\n\nAn attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a malformed `/FlateDecode` stream, where the byte-by-byte decompression is used.\n\n### Patches\n\nThis has been fixed in [pypdf==6.7.1](https://github.com/py-pdf/pypdf/releases/tag/6.7.1).\n\n### Workarounds\n\nIf you cannot upgrade yet, consider applying the changes from PR [#3644](https://github.com/py-pdf/pypdf/pull/3644).\n\n## Affected packages\n\n- `pypdf < 6.7.1`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `pypdf 6.7.1`","depth":"sunlit","depthScore":28,"depthScoreParts":{"impact":27.5,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}