How severe is CVE-2015-6420?

No CVSS score has been assigned to CVE-2015-6420 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2015-6420?

CVE-2015-6420 affects the following packages: org.apache.commons:commons-collections4 (Maven), commons-collections:commons-collections (Maven), net.sourceforge.collections:collections-generic (Maven), org.apache.servicemix.bundles:org.apache.servicemix.bundles.collections-generic (Maven), org.apache.servicemix.bundles:org.apache.servicemix.bundles.commons-collections (Maven). Ecosystems affected: Maven.

How do I fix CVE-2015-6420?

Update org.apache.commons:commons-collections4 to 4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2015-6420 is resolved across your whole dependency graph.

How do I detect CVE-2015-6420 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.commons:commons-collections4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2015-6420 if there is no patch (or I can't update yet)?

Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Is CVE-2015-6420 actively exploited in the wild?

No public exploit code has been indexed for CVE-2015-6420 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2015-6420?

CVE-2015-6420 has an EPSS (Exploit Prediction Scoring System) score of 15.2%, placing it in the 97th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

What type of vulnerability is CVE-2015-6420?

CVE-2015-6420 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2015-6420 published, and has it been updated?

CVE-2015-6420 was published on June 15, 2020 and was last updated on November 28, 2024. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2015-6420 — commons-collections4

CVE-2015-6420 is a Deserialization of Untrusted Data vulnerability in org.apache.commons:commons-collections4. EPSS puts its 30-day exploitation probability at 15.2% (97th percentile). A fix is available for org.apache.commons:commons-collections4 — see the affected versions and patch details below.

Insecure Deserialization in Apache Commons Collection

Published

Jun 15, 2020

Updated

Nov 28, 2024

Affected

5 pkgs

Patched

2 / 5

Exploits

None indexed

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2015-6420.

EPSS Exploitation Probability

via FIRST.org ↗

15.2%probability of exploitation in next 30 days

Moderate Risk0.00%

Lower risk than most CVEs97th percentile — riskier than 97% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

5 pkgs affected

☕org.apache.commons:commons-collections4☕commons-collections:commons-collections☕net.sourceforge.collections:collections-generic☕org.apache.servicemix.bundles:org.apache.servicemix.bundles.collections-generic☕org.apache.servicemix.bundles:org.apache.servicemix.bundles.commons-collections

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Serialized-object interfaces in certain Cisco Collaboration and Social Media; Endpoint Clients and Client Software; Network Application, Service, and Acceleration; Network and Content Security Devices; Network Management and Provisioning; Routing and Switching - Enterprise and Service Provider; Unified Computing; Voice and Unified Communications Devices; Video, Streaming, TelePresence, and Transcoding Devices; Wireless; and Cisco Hosted Services products allow remote attackers to execute arbitrary commands via a crafted serialized Java object, related to the Apache Commons Collections (ACC) library.

Affected Packages

5 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.commons:commons-collections4`	all versions	4.1`org.apache.commons:commons-collections4:4.1`
☕Maven	`commons-collections:commons-collections`	all versions	3.2.2`commons-collections:commons-collections:3.2.2`
☕Maven	`net.sourceforge.collections:collections-generic`	all versions	No fix
☕Maven	`org.apache.servicemix.bundles:org.apache.servicemix.bundles.collections-generic`	all versions	No fix
☕Maven	`org.apache.servicemix.bundles:org.apache.servicemix.bundles.commons-collections`	all versions	No fix

Affected Products

1 product · 2 configurations

Application

commons collectionsapache

≥ 3.0 && < 3.2.2

1 version

4.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.commons:commons-collections4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.apache.commons:commons-collections4 to 4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2015-6420 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

Serialized-object interfaces in Java applications using the Apache Commons Collections (ACC) library may allow remote attackers to execute arbitrary commands via a crafted serialized Java object.

O3 Security · Impact-Aware SCA

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