How severe is CVE-2016-4000?

CVE-2016-4000 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2016-4000 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2016-4000?

CVE-2016-4000 primarily affects Jython Project Jython. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2016-4000?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2016-4000 published?

CVE-2016-4000 was published on 2017-07-06 and last updated on 2026-06-17.

CVE-2016-4000

CVE-2016-4000 is a critical-severity vulnerability in Jython Project Jython with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-502.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 7% (93rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-502
Affected product: Jython Project Jython
Published: 2017-07-06
Last modified: 2026-06-17

Description

Jython before 2.7.1rc1 allows attackers to execute arbitrary code via a crafted serialized PyFunction object.

Frequently asked questions

What is CVE-2016-4000?: Jython before 2.7.1rc1 allows attackers to execute arbitrary code via a crafted serialized PyFunction object.
How severe is CVE-2016-4000?: CVE-2016-4000 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2016-4000 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 7% (93rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-4000?: CVE-2016-4000 primarily affects Jython Project Jython. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-4000?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2016-4000 published?: CVE-2016-4000 was published on 2017-07-06 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:jython_project:jython:2.7.0:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*

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