# CVE-2025-34037 — Linksys E4200

> As of 2026-07-22, CVE-2025-34037 is a Critical-severity (band derived from the CVSS v4.0 score, not stated by the CNA) vulnerability in Linksys E4200, CVSS v4.0 10, EPSS 92.7% (99.8th percentile). Threadlinqs Intelligence links 3 tracked threat campaigns to CVE-2025-34037, most recently “ClingSTUN Linux Backdoor Turns Unpatched IoT Devices Into Proxy Nodes via Public STUN Infrastructure”.

**Last updated:** 2026-07-22

## What is CVE-2025-34037?

An OS command injection vulnerability exists in various models of E-Series Linksys routers via the /tmUnblock.cgi and /hndUnblock.cgi endpoints over HTTP on port 8080. The CGI scripts improperly process user-supplied input passed to the ttcp_ip parameter without sanitization, allowing unauthenticated attackers to inject shell commands. This vulnerability was reported to be exploited in the wild by the "TheMoon" worm in 2014 to deploy a MIPS ELF payload, enabling arbitrary code execution on the router. Additionally, this vulnerability may affect other Linksys products to include, but not limited to, WAG/WAP/WES/WET/WRT-series router models and Wireless-N access points and routers. Exploitation evidence was observed by the Shadowserver Foundation on 2025-02-06 UTC.

The record classifies CVE-2025-34037 under weakness class [CWE-78](https://intel.threadlinqs.com/cwe/CWE-78). 11 affected-product entries are recorded, across 1 vendor, listed below. The identifier was first published 487 days ago.

## Severity and exploitation probability

- **CVSS v4.0 base score:** 10 — Critical (derived from score) (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`)
- **EPSS (FIRST):** 92.7% probability of exploitation in the next 30 days, higher than 99.8% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 10/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2025-06-24, last modified 2026-07-22

## Is CVE-2025-34037 being exploited?

Weaponised exploit code for CVE-2025-34037 is publicly available. 2 public proof-of-concept repositories are tracked for this identifier. It currently carries a trending score of 43 in the Threadlinqs vulnerability feed.

- [Taxanehh/CVE-2025-34037](https://github.com/Taxanehh/CVE-2025-34037) (github)
- [trickest/cve](https://github.com/trickest/cve/blob/main/2025/CVE-2025-34037.md) (trickest)

## Affected products and versions

- **Linksys**: E4200, E3200, E3000, E2500 v1/v2, E2100L v1, E2000, E1550, E1500 v1, E1200 v1, E1000 v1, E900 v1

## How to fix CVE-2025-34037

No vendor patch reference has been recorded for CVE-2025-34037 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-2025-34037

3 tracked threats in the Threadlinqs corpus reference CVE-2025-34037, either in the campaign’s CVE list or as an indicator on the campaign record.

- [ClingSTUN Linux Backdoor Turns Unpatched IoT Devices Into Proxy Nodes via Public STUN Infrastructure](https://intel.threadlinqs.com/threat/TL-2026-2934) — HIGH · 2026-10-05
- [Cling IoT botnet masquerades as Google STUN traffic for C2, exploiting Realtek Jungle SDK CVE-2021-35394](https://intel.threadlinqs.com/threat/TL-2026-2857) — CRITICAL · 2026-10-03
- [TuxBot v3 Evolution: LLM-Assisted IoT Botnet Framework With a Broken Multi-CVE Exploit Chain](https://intel.threadlinqs.com/threat/TL-2026-1366) — HIGH · 2026-07-15

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-10-10. This product uses the NVD API but is not endorsed or certified by the NVD.

**Exploit and proof of concept**

- [exploit-db.com — third party advisory](https://www.exploit-db.com/exploits/31683)

**Technical analysis**

- [isc.sans.edu — technical description](https://isc.sans.edu/diary/17633)

**Third-party advisory**

- [vulncheck.com — third party advisory](https://vulncheck.com/advisories/linksys-routers-command-injection)

Canonical: https://intel.threadlinqs.com/cve/CVE-2025-34037
Full detection coverage and IOCs for threats exploiting CVE-2025-34037 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp