CVE-2026-71852 — pypdf
Fix: py-pdf/pypdf@51cb6acCVE-2026-71852 is a CWE-834 vulnerability in pypdf. A fix is available for pypdf — see the affected versions and patch details below.
pypdf: Possible long runtimes/large memory usage for large CID font width ranges
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-71852.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
pypdfReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
An attacker who uses this vulnerability can craft a PDF which leads to long runtimes and large memory consumption. This requires parsing the font width entries of a font with unusually large values, for example during text extraction.
Patches
This has been fixed in pypdf==6.15.0.
Workarounds
If you cannot upgrade yet, consider applying the changes from PR #3946.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pypdf | all versions | 6.15.0pip install --upgrade 'pypdf==6.15.0' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pypdf, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pypdf to 6.15.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-71852 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-71852 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-71852. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This Moderate impact denial-of-service vulnerability in the pypdf library can lead to excessive memory consumption and long runtimes when processing specially crafted PDF files. This issue affects Red Hat products that handle untrusted PDF input, potentially causing service disruption due to resource exhaustion.…
To reduce exposure, avoid processing untrusted PDF documents with applications that integrate the pypdf library. Implement robust input validation and sanitization for all PDF files originating from external or unverified sources. Consider deploying applications that process PDF content within a sandboxed environment to contain potential denial of service impacts.Source: Red Hat security advisory for CVE-2026-71852 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-71852 in your dependencies?
O3 Security finds CVE-2026-71852 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.