How severe is CVE-2016-4437?

CVE-2016-4437 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2016-4437?

CVE-2016-4437 affects the following packages: org.apache.shiro:shiro-core (Maven). Ecosystems affected: Maven.

How do I fix CVE-2016-4437?

Update org.apache.shiro:shiro-core to version 1.2.5 or later. Run your dependency manager's update command and verify no transitive dependencies pin the vulnerable version. Use O3 Security's SCA scanner to confirm the fix is applied across your entire dependency tree.

Is CVE-2016-4437 actively exploited in the wild?

Yes. There are 10 known exploit references for CVE-2016-4437, including 1 documented proof-of-concept exploit on Exploit-DB and 6 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2016-4437?

CVE-2016-4437 has an EPSS (Exploit Prediction Scoring System) score of 94.3%, placing it in the 100th 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. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2016-4437 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2016-4437 (Apache Shiro Code Execution Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-05-03. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2016-4437?

CVE-2016-4437 is classified as CWE-321 (CWE-321). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2016-4437?

A Nuclei detection template exists for CVE-2016-4437, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2016-4437 published, and has it been updated?

CVE-2016-4437 was published on June 7, 2016 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2021-11-03 — agencies required to remediate by 2022-05-03

☕ Maven

CVE-2016-4437

CRITICAL

Improper Access Control in Apache Shiro

Also known asGHSA-p836-389h-j692

Published

Jun 7, 2016

Updated

Apr 10, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

10 known

EPSS Exploitation Probability

via FIRST.org ↗

94.3%probability of exploitation in next 30 days

Very High Risk100th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

☕org.apache.shiro:shiro-core

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

Apache Shiro before 1.2.5, when a cipher key has not been configured for the "remember me" feature, allows remote attackers to execute arbitrary code or bypass intended access restrictions via an unspecified request parameter.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.shiro:shiro-core`	all versions	1.2.5

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-48410remotemultiple✓ Verified

Apache Shiro 1.2.4 - Cookie RememberME Deserial RCE (Metasploit)

by Metasploit · May 1, 2020

Exploit-DB Source

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2016-4437 in your stack?

O3 detects CVE-2016-4437 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my stack How O3 SCA works