CVE-2026-71870 pypdf: Possible large memory usage for large /ToUnicode streams
Attackers can cause excessive memory consumption in pypdf by crafting PDFs with large /ToUnicode streams, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-71870?
CVE-2026-71870 is a medium-severity denial of service vulnerability in Pypdf Project Pypdf, published on 7 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Official description
pypdf is a free and open-source pure-python PDF library. Prior to 6.15.0, a crafted PDF can cause large memory consumption when pypdf/_cmap.py function parse_bfrange parses unusually large source-code or destination-string tokens in a font /ToUnicode CMap during text extraction. This issue is fixed in 6.15.0.
Weakness: CWE-400
Which versions are affected by CVE-2026-71870?
3 open source packages ship an affected version, including pypdf. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
pypdf PyPI | All versions | 6.15.0 |
pypdf PyPI | All versions | 6.15.0 |
pypdf PyPI | All versions | 6.15.0 |
Linux distribution packages (1)
python-pypdf openSUSE:Tumbleweed | All versions | 6.16.2-1.1 |
Products include Pypdf Project Pypdf.
How do I fix CVE-2026-71870?
Upgrade pypdf to 6.15.0 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-71870 being exploited?
There is no known exploitation of CVE-2026-71870 in the wild and no public exploit code.
Other vulnerabilities in Pypdf Project Pypdf
- CVE-2026-102993 pypdf: Possible large memory usage when retrieving Roman page labels
- CVE-2026-102994 pypdf: Possible long runtimes/large memory usage when parsing indirect objects
- CVE-2026-102995 pypdf: Possible large memory usage for large /ToUnicode streams (Follow-up 2)
- CVE-2026-102996 pypdf: Possible large memory usage when parsing font data
- CVE-2026-102997 pypdf: Possible long runtimes for partially malformed FlateDecode streams (Follow-up)
Sources
Also known as CLEANSTART-2026-YN75151, DEBIAN-CVE-2026-71870, ECHO-914b-f001-9bd1, GHSA-fp3f-mc75-235c, MINI-2p7x-v96q-4cgx, MINI-3pmc-p293-g8px and 16 more.