CVE-2021-41653
Published: April 11, 2026
Official Description
The PING function on the TP-Link TL-WR840N EU v5 router with firmware through TL-WR840N(EU)_V5_171211 is vulnerable to remote code execution via a crafted payload in an IP address input field.
Risk Analysis
This vulnerability allows an attacker to execute malicious code on the TP-Link TL-WR840N EU v5 router by sending a specially crafted IP address to the PING function. Its inclusion in CISA's KEV catalog indicates confirmed exploitation, making it an urgent threat.
Active exploitation of this vulnerability has been observed in the wild. The flaw is remotely exploitable, allowing attackers to compromise affected devices without direct physical access.
Update the TP-Link TL-WR840N EU v5 router firmware to a version beyond TL-WR840N(EU)_V5_171211. Regularly apply security updates to network devices and restrict access to administrative interfaces.
Technical Analysis
CVE-2021-41653 requires local access, meaning attackers must already have a foothold on the target system.
Exploitation requires some privileges, which limits the exposure to scenarios where an attacker has already gained initial access.
CISA has added CVE-2021-41653 to the Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. U.S. federal agencies are required to patch this within the mandated timeframe, and all organizations should treat remediation as urgent.
Exploit & PoC Resources
Quick Facts
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-41653 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts
- !CISA KEV: Federal agencies must patch per BOD 22-01 timeline
- !Active exploitation confirmed — treat as P1