CVE-2026-31826: pypdf Manipulated Stream Length Values Can Vulnerability

MODERATE
Advisory Identifier: GHSA-hqmh-ppp3-xvm7
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CWE-770
Published
Advisory Summary

CVE-2026-31826 is a MODERATE manipulated stream length values can vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting pypdf libraries in the PyPI ecosystem. The issue involves manipulated stream length values can exhaust ram. Remediation is available by upgrading affected packages to version 6.8.0.

CVE-2026-31826 at a Glance

CVE Identifier CVE-2026-31826
GHSA Identifier GHSA-hqmh-ppp3-xvm7
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product pypdf
Package Ecosystem PyPI
Published Date
Last Updated

How to Fix CVE-2026-31826

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: 6.8.0 
pip install pypdf>=6.8.0
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-2026-31826, 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 6.8.0), 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-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. 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 large memory usage. This requires parsing a content stream with a rather large `/Length` value, regardless of the actual data length inside the stream. ### Patches This has been fixed in [pypdf==6.8.0](https://github.com/py-pdf/pypdf/releases/tag/6.8.0). ### Workarounds If you cannot upgrade yet, consider applying the changes from PR [#3675](https://github.com/py-pdf/pypdf/pull/3675). As far as we are aware, this mostly affects reading from buffers of unknown size, as returned by `open("file.pdf", mode="rb")` for example. Passing a file path or a `BytesIO` buffer to *pypdf* instead does not seem to trigger the vulnerability.

CVE-2026-31826 Affected pypdf Versions

1 component(s)
Fixed Versions:
6.8.0
Product / Package Ecosystem Affected Versions Fixed Version
pypdf
pypi/pypdf
PyPI
< 6.8.0
6.8.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/py-pdf/pypdf/security/advisories/GHSA-hqmh-ppp3-xvm7
NVD — CVE-2026-31826 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-31826
pypdf Source Repository REPOSITORY
https://github.com/py-pdf/pypdf/pull/3675
Security Fix Commit FIX COMMIT
https://github.com/py-pdf/pypdf/commit/3c550b3196adeba1506a26e57c09c09fac75e9aa
pypdf Source Repository REPOSITORY
https://github.com/py-pdf/pypdf
pypdf Release RELEASE
https://github.com/py-pdf/pypdf/releases/tag/6.8.0

Frequently Asked Questions

What is CVE-2026-31826?
CVE-2026-31826 is a security vulnerability in pypdf involving manipulated stream length values can exhaust RAM under CWE-770: Allocation of Resources Without Limits or Throttling.
Which pypdf versions are affected?
Affected versions include releases prior to 6.8.0 across affected packages: pypdf.
What version fixes CVE-2026-31826?
Upgrading to 6.8.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is pypdf affected?
Yes, pypdf is affected in releases prior to 6.8.0. Upgrade your dependency to 6.8.0 or later.
What CWE is associated with CVE-2026-31826?
CVE-2026-31826 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check PyPI dependencies for CVE-2026-31826?
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-hqmh-ppp3-xvm7",
  "modified" : "2026-03-11T05:46:57Z",
  "published" : "2026-03-11T00:14:02Z",
  "aliases" : [ "CVE-2026-31826" ],
  "summary" : "pypdf: manipulated stream length values can exhaust RAM",
  "details" : "### Impact\n\nAn attacker who uses this vulnerability can craft a PDF which leads to large memory usage. This requires parsing a content stream with a rather large `/Length` value, regardless of the actual data length inside the stream.\n\n### Patches\nThis has been fixed in [pypdf==6.8.0](https://github.com/py-pdf/pypdf/releases/tag/6.8.0).\n\n### Workarounds\nIf you cannot upgrade yet, consider applying the changes from PR [#3675](https://github.com/py-pdf/pypdf/pull/3675).\n\nAs far as we are aware, this mostly affects reading from buffers of unknown size, as returned by `open(\"file.pdf\", mode=\"rb\")` for example. Passing a file path or a `BytesIO` buffer to *pypdf* instead does not seem to trigger the vulnerability.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pypdf"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "6.8.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/security/advisories/GHSA-hqmh-ppp3-xvm7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-31826"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/pull/3675"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/commit/3c550b3196adeba1506a26e57c09c09fac75e9aa"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/py-pdf/pypdf"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/py-pdf/pypdf/releases/tag/6.8.0"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-11T00:14:02Z",
    "nvd_published_at" : "2026-03-10T22:16:20Z"
  }
}