CVE-2026-22691
MEDIUM5.3EPSS 0.02%pypdf has possible long runtimes for malformed startxref
Description
### Impact An attacker who exploits this vulnerability can craft a PDF which leads to possibly long runtimes for invalid `startxref` entries. When rebuilding the cross-reference table, PDF files with lots of whitespace characters become problematic. Only the non-strict reading mode is affected. ### Patches This has been fixed in [pypdf==6.6.0](https://github.com/py-pdf/pypdf/releases/tag/6.6.0). ### Workarounds ```python from pypdf import PdfReader, PdfWriter # Instead of reader = PdfReader("file.pdf") # use the strict mode: reader = PdfReader("file.pdf", strict=True) # Instead of writer = PdfWriter(clone_from="file.pdf") # use an explicit strict reader: writer = PdfWriter(clone_from=PdfReader("file.pdf", strict=True)) ``` ### Resources This issue has been fixed in #3594.
Affected packages (3)
- Debian/pypdffrom 0
- Debian/pypdf2from 0
- PyPI/pypdffrom 0, < 6.6.0
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 4.0 | — | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U |
| osv | CVSS 3.1 | MEDIUM5.3 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L |
References (7)
- ADVISORYhttps://nvd.nist.gov/vuln/detail/CVE-2026-22691
- ADVISORYhttps://security-tracker.debian.org/tracker/CVE-2026-22691
- PATCHhttps://github.com/py-pdf/pypdf
- WEBhttps://github.com/py-pdf/pypdf/commit/294165726b646bb7799be1cc787f593f2fdbcf45
- WEBhttps://github.com/py-pdf/pypdf/pull/3594
- WEBhttps://github.com/py-pdf/pypdf/releases/tag/6.6.0
- WEBhttps://github.com/py-pdf/pypdf/security/advisories/GHSA-4f6g-68pf-7vhv