CVE-2026-82398: pypdf Inefficient Handling Of Non-whitespace Inputs Vulnerability

MODERATE
Advisory Identifier: GHSA-fc8x-2rww-xw9m
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CWE-407
Published
Advisory Summary

CVE-2026-82398 is a MODERATE inefficient handling of non-whitespace inputs vulnerability (CWE-407: Inefficient Algorithmic Complexity) affecting pypdf libraries in the PyPI ecosystem. The issue involves inefficient handling of non-whitespace inputs in read_until_whitespace. Remediation is available by upgrading affected packages to version 6.15.0.

CVE-2026-82398 at a Glance

CVE Identifier CVE-2026-82398
GHSA Identifier GHSA-fc8x-2rww-xw9m
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-407: Inefficient Algorithmic Complexity
Affected Product pypdf
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix CVE-2026-82398

To remediate this vulnerability, upgrade all affected pypdf dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

pypdf fixed: 6.15.0 
pip install pypdf>=6.15.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show pypdf

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-82398, inspect your installed packages using pip:

pip show pypdf

Analyze the terminal output to locate any version of pypdf in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.15.0), your application is affected.

Note: The pip show pypdf command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-407: Inefficient Algorithmic Complexity, where an algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached. In pypdf, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact An attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a call to `read_until_whitespace` with an input which does not have whitespace for a long time. ### 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 [#3947](https://github.com/py-pdf/pypdf/pull/3947).

CVE-2026-82398 Affected pypdf Versions

1 component(s)
Fixed Versions:
6.15.0
Product / Package Ecosystem Affected Versions Fixed Version
pypdf
pypi/pypdf
PyPI
< 6.15.0
6.15.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/py-pdf/pypdf/security/advisories/GHSA-fc8x-2rww-xw9m
NVD — CVE-2026-82398 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-82398
pypdf Source Repository REPOSITORY
https://github.com/py-pdf/pypdf/pull/3947
Security Fix Commit FIX COMMIT
https://github.com/py-pdf/pypdf/commit/4959848e057e37c218dccad7465259210923faaa
pypdf Source Repository REPOSITORY
https://github.com/py-pdf/pypdf
pypdf Release RELEASE
https://github.com/py-pdf/pypdf/releases/tag/6.15.0

Frequently Asked Questions

What is CVE-2026-82398?
CVE-2026-82398 is a security vulnerability in pypdf involving Inefficient handling of non-whitespace inputs in read_until_whitespace under CWE-407: Inefficient Algorithmic Complexity.
Which pypdf versions are affected?
Affected versions include releases prior to 6.15.0 across affected packages: pypdf.
What version fixes CVE-2026-82398?
Upgrading to 6.15.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pypdf affected?
Yes, pypdf is affected in releases prior to 6.15.0. Upgrade your dependency to 6.15.0 or later.
What CWE is associated with CVE-2026-82398?
CVE-2026-82398 is classified under CWE-407: Inefficient Algorithmic Complexity (An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.).
How can I check PyPI dependencies for CVE-2026-82398?
Run the dependency tree command: 'pip show pypdf'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-fc8x-2rww-xw9m",
  "modified" : "2026-09-02T14:38:12Z",
  "published" : "2026-09-02T14:38:12Z",
  "aliases" : [ "CVE-2026-82398" ],
  "summary" : "pypdf: Inefficient handling of non-whitespace inputs in read_until_whitespace",
  "details" : "### Impact\nAn attacker who uses this vulnerability can craft a PDF which leads to long runtimes. This requires a call to `read_until_whitespace` with an input which does not have whitespace for a long time.\n\n### Patches\nThis has been fixed in [pypdf==6.15.0](https://github.com/py-pdf/pypdf/releases/tag/6.15.0).\n\n### Workarounds\nIf you cannot upgrade yet, consider applying the changes from PR [#3947](https://github.com/py-pdf/pypdf/pull/3947).",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pypdf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.15.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/security/advisories/GHSA-fc8x-2rww-xw9m"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-82398"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/pull/3947"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/commit/4959848e057e37c218dccad7465259210923faaa"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/py-pdf/pypdf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/releases/tag/6.15.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-407" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-02T14:38:12Z",
    "nvd_published_at" : "2026-08-31T22:17:23Z"
  }
}