Threat Intelligence / CVE / CVE-2016-4437

CVE-2016-4437 — Apache Shiro

CISA KEV
CVSS v3.1 9.8 (CRITICAL) · EPSS 93.1% (higher than 99.8% of all scored CVEs) · Priority 9/10 · Published 2016-06-07

As of 2025-10-21, CVE-2016-4437 is a CRITICAL-severity vulnerability in Apache Shiro, CVSS v3.1 9.8, EPSS 93.1% (99.8th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), with a US federal remediation deadline of 2022-05-03. Threadlinqs Intelligence links 4 tracked threat campaigns to CVE-2016-4437, most recently “Chinese-Speaking Operator "Nie" Uses SecFlow AI Orchestration Framework (Claude, Qwen, DeepSeek) and GLUTTON Steganographic Webshell in Multi-Country Espionage Campaign”.

Last updated: 2025-10-21

What is CVE-2016-4437?

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.

The record classifies CVE-2016-4437 under weakness class CWE-321. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 4 affected-product entries are recorded, across 2 vendors, listed below. The identifier was first published 3750 days ago.

Severity and exploitation probability

CVSS v3.1 base score
9.8 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS (FIRST)
93.1% probability of exploitation in the next 30 days, higher than 99.8% of all scored CVEs
CISA KEV
Listed since 2021-11-03, federal remediation deadline 2022-05-03
Threadlinqs priority
9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published
2016-06-07, last modified 2025-10-21

Is CVE-2016-4437 being exploited?

CISA added CVE-2016-4437 to the Known Exploited Vulnerabilities catalog on 2021-11-03, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2022-05-03 under BOD 22-01. Weaponised exploit code for CVE-2016-4437 is publicly available. 7 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (http/cves/2016/CVE-2016-4437.yaml). It currently carries a trending score of 45 in the Threadlinqs vulnerability feed.

Affected products and versions

Affected software packages:

How to fix CVE-2016-4437

Fixed versions are recorded for 1 package: maven:org.apache.shiro:shiro-core 1.2.5. Because CVE-2016-4437 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2022-05-03. No vendor patch reference has been recorded for CVE-2016-4437 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

Threat activity tracking CVE-2016-4437

4 tracked threats in the Threadlinqs corpus reference CVE-2016-4437, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.

Vendor advisory and patch

Vulnerability database entry

Mailing list and disclosure

Other references

Full detection coverage & IOCs for threats exploiting CVE-2016-4437 are available via the Threadlinqs MCP server (Purple tier). View plans →

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