How severe is CVE-2026-71870?

No CVSS score has been assigned to CVE-2026-71870 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-71870?

CVE-2026-71870 affects the following packages: pypdf (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-71870?

Update pypdf to 6.15.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-71870 is resolved across your whole dependency graph.

How do I detect CVE-2026-71870 in my PyPI dependencies?

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.

How do I mitigate CVE-2026-71870 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2026-71870 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-71870 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-71870?

CVE-2026-71870 has an EPSS (Exploit Prediction Scoring System) score of 0.1%, placing it in the 2th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-71870?

CVE-2026-71870 is classified as Uncontrolled Resource Consumption (CWE-400). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-71870 published, and has it been updated?

CVE-2026-71870 was published on August 7, 2026 and was last updated on September 11, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-71870 — pypdf

Fix: py-pdf/pypdf@afba808

CVE-2026-71870 is a Uncontrolled Resource Consumption vulnerability in pypdf. A fix is available for pypdf — see the affected versions and patch details below.

pypdf: Possible large memory usage for large /ToUnicode streams

Also known asGHSA-fp3f-mc75-235cPYSEC-2026-3655

Published

Aug 7, 2026

Updated

Sep 11, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 6, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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-2026-71870.

EPSS Exploitation Probability

via FIRST.org ↗

0.1%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs2th percentile — riskier than 2% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐍pypdf

Real-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 large memory consumption. This requires parsing the /ToUnicode entry 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 #3944.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`pypdf`	all versions	6.15.0`pip install --upgrade 'pypdf==6.15.0'`

Affected Products

1 product · 1 configurations

Application

pypdfpypdf_project

< 6.15.0

range

Detection & mitigation playbook

Open-source dependency

Detect
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-2026-71870 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

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.

Red HatModerate

A flaw in the pypdf library can lead to a denial of service due to uncontrolled resource consumption. Processing a specially crafted PDF file containing unusually large /ToUnicode streams can cause excessive memory allocation, impacting the availability of Red Hat products that rely on pypdf for PDF processing. This…

Workaround published by Red Hat

To reduce exposure, avoid processing untrusted PDF files with applications that use the pypdf library. If processing untrusted content is necessary, deploy affected applications within a sandboxed environment to contain potential resource exhaustion.

Source: Red Hat security advisory for CVE-2026-71870 (CC BY 4.0)

Frequently Asked Questions

### Impact An attacker who uses this vulnerability can craft a PDF which leads to large memory consumption. This requires parsing the `/ToUnicode` entry of a font with unusually large values, for example during text extraction. ### Patches This has been fixed in [pypdf==6.15.0](https://github.com/py-pdf/pypdf/releases/tag/6.15.0). ### Workarounds If you cannot upgrade yet, consider applying the changes from PR [#3944](https://github.com/py-pdf/pypdf/pull/3944).

O3 Security · Impact-Aware SCA

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