CVE-2021-27245 : What You Need to Know

This article provides details about CVE-2021-27245, a vulnerability impacting TP-Link Archer A7 routers, allowing a firewall bypass. Find out about the vulnerability, its impact, technical details, and mitigation steps.

Understanding CVE-2021-27245

CVE-2021-27245 is a security vulnerability affecting TP-Link Archer A7 routers, enabling a firewall bypass without requiring authentication. The flaw lies in the handling of IPv6 connections, leading to potential code execution without user interaction.

What is CVE-2021-27245?

CVE-2021-27245 allows malicious actors to bypass firewalls on TP-Link Archer A7 routers by exploiting improper filtering of IPv6 SSH connections. This can grant threat actors root-level access without needing any user privileges.

The Impact of CVE-2021-27245

The vulnerability's impact is rated as high, with a CVSS base score of 8.1. It poses a significant threat to confidentiality, integrity, and availability as attackers can execute arbitrary code in a network context without any user interaction.

Technical Details of CVE-2021-27245

The vulnerability stems from a protection mechanism failure (CWE-693). Affected versions include TP-Link Archer A7 prior to Archer C7(US)_V5_210125 and Archer A7(US)_V5_200220 AC1750 routers. The flaw allows unauthenticated attackers to exploit improper IPv6 handling for SSH connections.

Vulnerability Description

The specific flaw in CVE-2021-27245 is the lack of adequate filtering for IPv6 SSH connections on TP-Link Archer A7 routers. This oversight enables threat actors to sidestep firewall protections and potentially achieve root-level access.

Affected Systems and Versions

TP-Link Archer A7 routers prior to Archer C7(US)_V5_210125 and Archer A7(US)_V5_200220 AC1750 models are affected by CVE-2021-27245. Users of these versions are at risk of unauthorized firewall bypass and code execution.

Exploitation Mechanism

Exploiting this vulnerability requires leveraging the improper handling of IPv6 connections on the affected routers. Attackers can combine this flaw with other vulnerabilities to gain elevated privileges and execute malicious code.

Mitigation and Prevention

To mitigate the risks associated with CVE-2021-27245, users should take immediate steps and adopt long-term security practices to secure their TP-Link Archer A7 routers.

Immediate Steps to Take

Immediately update the firmware of TP-Link Archer A7 routers to version Archer C7(US)_V5_210125 or newer to address this vulnerability. Disable remote management and ensure strong, unique passwords for router access.

Long-Term Security Practices

Regularly check for firmware updates and security advisories from TP-Link. Implement network segmentation and access controls to limit the impact of potential security breaches.

Patching and Updates

Apply patches and updates provided by TP-Link to fix CVE-2021-27245. Stay informed about security best practices and monitor for any unusual network activity that could indicate exploitation attempts.