pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
### Impact An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a partially malformed `/FlateDecode` stream, where the byte-by-byte decompression is used. ### Patches This has been fixed in [pypdf==6.18.1](https://github.com/py-pdf/pypdf/releases/tag/6.18.1). ### Workarounds If you cannot upgrade yet, consider applying the changes from PR [#4073](https://github.com/py-pdf/pypdf/pull/4073).
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describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-102997US | high7.5 | — | ||
pypdf is a free and open-source pure-python PDF library. Prior to 6.18.1, a crafted PDF containing a partially malformed /FlateDecode stream with padded data can force pypdf/filter… | ||||
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references
External citations — patches, advisories, analysis.
- https://github.com/py-pdf/pypdfPACKAGE
- https://github.com/py-pdf/pypdf/commit/d9d38cf99b115deb562d3b68f36c33027bc04f79WEB
- https://github.com/py-pdf/pypdf/pull/4073WEB
- https://github.com/py-pdf/pypdf/releases/tag/6.18.1WEB
- https://github.com/py-pdf/pypdf/security/advisories/GHSA-jw7q-gvrg-4vj3WEB
- https://nvd.nist.gov/vuln/detail/CVE-2026-102997ADVISORY
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