How severe is CVE-2025-66019?

No CVSS score has been assigned to CVE-2025-66019 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-66019?

CVE-2025-66019 affects the following packages: pypdf (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2025-66019?

Update pypdf to 6.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66019 is resolved across your whole dependency graph.

How do I detect CVE-2025-66019 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-2025-66019 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-2025-66019 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-66019 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-2025-66019?

CVE-2025-66019 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 33th 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-2025-66019?

CVE-2025-66019 is classified as Uncontrolled Resource Consumption (CWE-400), CWE-409 (CWE-409). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-66019 published, and has it been updated?

CVE-2025-66019 was published on November 25, 2025 and was last updated on October 28, 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-2025-66019 — pypdf

Fix: py-pdf/pypdf@9618672

CVE-2025-66019 is a Uncontrolled Resource Consumption vulnerability in pypdf. A fix is available for pypdf — see the affected versions and patch details below.

pypdf manipulated LZWDecode streams can exhaust RAM

Also known asGHSA-m449-cwjh-6pw7PYSEC-2026-1832

Published

Nov 25, 2025

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
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-2025-66019.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs33th percentile — riskier than 33% 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 a memory usage of up to 1 GB per stream. This requires parsing the content stream of a page using the LZWDecode filter.

This is a follow up to GHSA-jfx9-29x2-rv3j to align the default limit with the one for zlib.

Patches

This has been fixed in pypdf==6.4.0.

Workarounds

If users cannot upgrade yet, use the line below to overwrite the default in their code:

pypdf.filters.LZW_MAX_OUTPUT_LENGTH = 75_000_000

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`pypdf`	all versions	6.4.0`pip install --upgrade 'pypdf==6.4.0'`

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 6.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66019 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

Workaround published by Red Hat

Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Source: Red Hat security advisory for CVE-2025-66019 (CC BY 4.0)

Frequently Asked Questions

### Impact An attacker who uses this vulnerability can craft a PDF which leads to a memory usage of up to 1 GB per stream. This requires parsing the content stream of a page using the LZWDecode filter. This is a follow up to [GHSA-jfx9-29x2-rv3j](https://github.com/py-pdf/pypdf/security/advisories/GHSA-jfx9-29x2-rv3j) to align the default limit with the one for *zlib*. ### Patches This has been fixed in [pypdf==6.4.0](https://github.com/py-pdf/pypdf/releases/tag/6.4.0). ### Workarounds If users cannot upgrade yet, use the line below to overwrite the default in their code: ```python pypdf.

O3 Security · Impact-Aware SCA

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