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Critical, CVSS 9.8

Deserialization of Untrusted Data in Jython

CVE-2016-4000GHSA-6r7r-jj8h-pq6v

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (org.python:jython-standalone 2.7.1b3; org.python:jython 2.7.1b3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
9.8 · CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS
  • CVE-2016-4000: 6.21% estimated exploitation activity in the next 30 days; percentile 93.53 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Jython before 2.7.1b3 allows attackers to execute arbitrary code via a crafted serialized PyFunction object.

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 1 · created ·

    Published from ghsa record GHSA-6r7r-jj8h-pq6v

Agent brief

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# Patch Next advisory brief: CVE-2016-4000

Advisory: Deserialization of Untrusted Data in Jython
IDs: CVE-2016-4000, GHSA-6r7r-jj8h-pq6v
Record: https://patchnext.com/advisories/cve-2016-4000 (revision 1, source checked 26 Oct 2026, 16:54 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.python:jython-standalone 2.7.1b3; org.python:jython 2.7.1b3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.python:jython-standalone: affected < 2.7.1b3; fixed in 2.7.1b3
- Maven org.python:jython: affected < 2.7.1b3; fixed in 2.7.1b3

## Suggested inspection (read-only)
- Maven org.python:jython-standalone: check the installed version with your package manager.
- Maven org.python:jython: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.python:jython-standalone, org.python:jython.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6r7r-jj8h-pq6v (GitHub-reviewed advisory GHSA-6r7r-jj8h-pq6v lists affected ranges: Maven org.python:jython-standalone >=0 =0 <2.7.1b3)

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