pypdf: manipulated stream length values can exhaust RAM
Impact
An attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing a content stream with a rather large /Length value, regardless of the actual data length inside the stream.
Patches
This has been fixed in pypdf==6.8.0.
Workarounds
If you cannot upgrade yet, consider applying the changes from PR #3675.
As far as we are aware, this mostly affects reading from buffers of unknown size, as returned by open("file.pdf", mode="rb") for example. Passing a file path or a BytesIO buffer to pypdf instead does not seem to trigger the vulnerability.
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | pypdf | < 6.8.0 | 6.8.0 |
References
- https://github.com/py-pdf/pypdf/security/advisories/GHSA-hqmh-ppp3-xvm7
- https://nvd.nist.gov/vuln/detail/CVE-2026-31826
- https://github.com/py-pdf/pypdf/pull/3675
- https://github.com/py-pdf/pypdf/commit/3c550b3196adeba1506a26e57c09c09fac75e9aa
- https://github.com/py-pdf/pypdf
- https://github.com/py-pdf/pypdf/releases/tag/6.8.0
- https://pypi.org/project/pypdf
- https://github.com/advisories/GHSA-hqmh-ppp3-xvm7
- CVSS vector
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N- Weakness (CWE)
CWE-770- Platform
- Python (PyPI)
- Package
pypdf- Disclosed
- 11.03.2026
- Updated
- 11.10.2026 15:17
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2026-3019 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-hqmh-ppp3-xvm7 - CC BY 4.0
Vulnerability history: pypdf
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 51
- First → latest
- 06.2023 10.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 10
- Medium 38
- Low 3
Disclosures per year
- 2023: 2
- 2024: 0
- 2025: 4
- 2026: 45
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