# CVE-2016-4437 — Apache Shiro **CISA KEV** > 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](https://cwe.mitre.org/data/definitions/321.html). 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. - [bkfish/Awesome_shiro](https://github.com/bkfish/Awesome_shiro) (github) - [4nth0ny1130/shisoserial](https://github.com/4nth0ny1130/shisoserial) (github) - [pizza-power/CVE-2016-4437](https://github.com/pizza-power/CVE-2016-4437) (github) - [35789-gh/cve-2016-4437](https://github.com/35789-gh/cve-2016-4437) (github) - [m3terpreter/CVE-2016-4437](https://github.com/m3terpreter/CVE-2016-4437) (github) - [xk-mt/CVE-2016-4437](https://github.com/xk-mt/CVE-2016-4437) (github) - [trickest/cve](https://github.com/trickest/cve/blob/main/2016/CVE-2016-4437.md) (trickest) ## Affected products and versions - **Apache**: Aurora, Shiro - **Redhat**: Fuse 1.0, Jboss Middleware Text-only Advisories 1.0 Affected software packages: - `maven:org.apache.shiro:shiro-core` — patched in 1.2.5 ## 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. - [Chinese-Speaking Operator "Nie" Uses SecFlow AI Orchestration Framework (Claude, Qwen, DeepSeek) and GLUTTON Steganographic Webshell in Multi-Country Espionage Campaign](https://intel.threadlinqs.com/threat/TL-2026-2325) — HIGH · 2026-09-04 - [StrikeShark Campaign: SharkLoader Dropper Targets Governments and Software Developers via N-Day Exploits and Trojanized Installers to Deploy Cobalt Strike](https://intel.threadlinqs.com/threat/TL-2026-1237) — HIGH · 2026-07-11 - [SharkLoader Malware Campaign Uses Fake Cisco AnyConnect and Google Update Installers to Deploy Cobalt Strike](https://intel.threadlinqs.com/threat/TL-2026-1101) — HIGH · 2026-07-03 - [SharkLoader Malware Deploys Cobalt Strike Beacon via DLL Side-Loading in StrikeShark Campaign](https://intel.threadlinqs.com/threat/TL-2026-0961) — HIGH · 2026-06-27 ## 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 2026-06-28. This product uses the NVD API but is not endorsed or certified by the NVD. **Vendor advisory and patch** - [rhn.redhat.com — vendor advisory](http://rhn.redhat.com/errata/RHSA-2016-2035.html) - [rhn.redhat.com — vendor advisory (RHSA 2016 2036)](http://rhn.redhat.com/errata/RHSA-2016-2036.html) **Vulnerability database entry** - [securityfocus.com — vdb entry](http://www.securityfocus.com/bid/91024) **Mailing list and disclosure** - [lists.apache.org — mailing list](https://lists.apache.org/thread.html/ef3a800c7d727a00e04b78e2f06c5cd8960f09ca28c9b69d94c3c4c4%40%3Cannouncements.aurora.apache.org%3E) - [securityfocus.com — mailing list](http://www.securityfocus.com/archive/1/538570/100/0/threaded) **Other references** - [packetstormsecurity.com](http://packetstormsecurity.com/files/137310/Apache-Shiro-1.2.4-Information-Disclosure.html) - [packetstormsecurity.com (Apache Shiro 1.2.4 Remote Code Execution)](http://packetstormsecurity.com/files/157497/Apache-Shiro-1.2.4-Remote-Code-Execution.html) Canonical: https://intel.threadlinqs.com/cve/CVE-2016-4437 Full detection coverage and IOCs for threats exploiting CVE-2016-4437 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp