NVD / CVE Program· CNA GitHub_M

CVE-2025-66019: pypdf manipulated LZWDecode streams can exhaust RAM

Noroxi assessment

Priority: Monitor (action score 26/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.38% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: py-pdf pypdf 6.4.0.

Low priority for now. Upgrade to py-pdf pypdf 6.4.0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

pypdf is a free and open-source pure-python PDF library. Prior to version 6.4.0, 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 issue has been patched in version 6.4.0.

MediumCVSS 6.6 · v4.0—No exploit Fix available

Published: Nov 26, 2025
Updated: Oct 19, 2026
EPSS: 0.3% · 32th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 26 / 40 · 6.6 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.3%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · GitHub_M: 6.6; NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

py-pdf pypdf
- < 6.4.0affected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
openSUSE:Tumbleweed	python-pypdf	before 6.4.0-1.1	6.4.0-1.1
PyPI	pypdf	before 6.4.0	6.4.0

Same product

py-pdf: all records

Other highest-scoring records for the same primary product.

CVE-2026-119209pypdf: Possible large memory usage when parsing cross-reference streams
28Monitor
CVE-2026-119208pypdf: Possible long runtimes/large memory usage for encrypted PDF files
28Monitor
CVE-2026-119207pypdf: Possible large memory usage for exceptions in strict mode
28Monitor

Published before and after this one in the same product

Later →CVE-2026-113786Oct 21, 2026 · pypdf: Unvalidated JPEG image data loading
9Monitor
Later →CVE-2026-113789Oct 21, 2026 · pypdf: Possible long runtimes/large memory usage when retrieving form fields
24Monitor
Later →CVE-2026-113790Oct 21, 2026 · pypdf: Possible large memory usage when parsing arrays and dictionaries
24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
py-pdf pypdf	6.4.0 · description	Vendor (CNA)
opensuse:python-pypdf	6.4.0-1.1 · openSUSE:Tumbleweed	Package registry (OSV)
PyPI:pypdf	6.4.0	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

py-pdf/pypdfcommit 9618672

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-115572331 days apartpypdf: Possible long runtimes for repeated references to the same missing object
28Monitor
CVE-2026-115585331 days apartpypdf: Possible long runtimes for repeated malformed cross-reference entries (Follow-up)
28Monitor
CVE-2026-119204337 days apartpypdf: Possible large memory usage when parsing page tree
28Monitor
CVE-2026-119207337 days apartpypdf: Possible large memory usage for exceptions in strict mode
28Monitor
CVE-2026-119208337 days apartpypdf: Possible long runtimes/large memory usage for encrypted PDF files
28Monitor
CVE-2026-119209337 days apartpypdf: Possible large memory usage when parsing cross-reference streams
28Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: X

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

Fix✗ → ✓Sep 28, 2026, 10:46 PM UTC

For records you follow, these changes also arrive as notifications. →

References

github.com/py-pdf/pypdf/commit/96186725e5e6f237129a58a97cd19204a9ce40b2

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records