TL;DR
Cybersecurity authorities have confirmed that attackers are actively exploiting CVE-2021-27137, a stack-based buffer overflow in DD-WRT firmware. This vulnerability affects routers using DD-WRT, allowing remote code execution without authentication. The development raises urgent security concerns for affected users.
Cybersecurity authorities have confirmed that attackers are actively exploiting CVE-2021-27137, a stack-based buffer overflow vulnerability in DD-WRT firmware. This flaw allows an unauthenticated attacker to execute arbitrary code on affected devices by exploiting the UPnP component. The active exploitation increases the risk for thousands of routers worldwide, highlighting an urgent security threat.
According to the Cybersecurity and Infrastructure Security Agency (CISA), CVE-2021-27137 is being exploited in the wild to compromise DD-WRT routers. The vulnerability resides in the firmware’s UPnP (Universal Plug and Play) service, where an unchecked buffer allows attackers to execute arbitrary code remotely. Experts warn that this could lead to full device control, enabling malicious activities such as data theft, network manipulation, or further malware deployment. The vulnerability was initially disclosed in 2021, but recent reports and security advisories confirm that active exploitation has resumed or intensified. The attackers are exploiting the flaw to gain persistent access, with some evidence suggesting automated scanning and attack campaigns targeting routers with exposed UPnP services. DD-WRT users are urged to update their firmware immediately, if patches are available, or disable UPnP if updates are not yet released.Impact of Active Exploitation on Network Security
The active exploitation of CVE-2021-27137 poses a significant risk to network security globally. DD-WRT is widely used in consumer and small business routers, often with minimal security configurations. Successful exploitation can lead to full remote control of affected devices, enabling attackers to intercept traffic, launch further attacks within networks, or use compromised routers as part of larger botnet operations. This situation underscores the importance of timely firmware updates and security monitoring for network devices.
DD-WRT router firmware update
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
Background and Past Disclosures of CVE-2021-27137
CVE-2021-27137 was originally disclosed in late 2021 as a stack-based buffer overflow vulnerability affecting DD-WRT firmware, specifically targeting the UPnP service. The flaw allows unauthenticated attackers to overflow internal buffers and execute arbitrary code remotely. While patches and mitigations were issued initially, subsequent security reports indicated that many devices remained vulnerable due to outdated firmware or unpatched configurations.
Recent security alerts from CISA and other cybersecurity firms confirm that threat actors are now actively exploiting this known vulnerability, which had been dormant or under the radar for some time. This resurgence of exploitation highlights ongoing challenges in patch management and device security in the consumer router ecosystem.
“The active exploitation of CVE-2021-27137 underscores the need for immediate firmware updates and security awareness among users of DD-WRT devices.”
— CISA spokesperson
TP-Link ER707-M2 | Omada Multi-Gigabit VPN Router | Dual 2.5Gig WAN Ports | High Network Capacity | SPI Firewall | Omada SDN Integrated | Load Balance | Lightning Protection
【Flexible Port Configuration】1 2.5Gigabit WAN Port + 1 2.5Gigabit WAN/LAN Ports + 4 Gigabit WAN/LAN Port + 1…
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
Extent and Scope of the Current Exploitation Campaign
It is not yet clear how widespread the active exploitation is or which specific attacker groups are involved. Details about the scale, targeted regions, or specific payloads used in the campaigns remain under investigation. Security firms are monitoring ongoing attack patterns, but comprehensive data is still emerging.
TP-Link ER605 V2 Wired Gigabit VPN Router, Up to 3 WAN Ethernet Ports + 1 USB WAN, SPI Firewall SMB Router, Omada SDN Integrated, Load Balance, Lightning Protection
【Five Gigabit Ports】1 Gigabit WAN Port plus 2 Gigabit WAN/LAN Ports plus 2 Gigabit LAN Port. Up to…
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
Recommended Actions and Future Security Measures
Affected users should verify their firmware version and apply updates or disable UPnP if patches are unavailable. Security agencies and vendors are expected to release advisories with mitigation steps. Ongoing monitoring of attack activity and further research into attacker methods are also anticipated. Experts recommend regular firmware updates and network security audits to reduce risk.
UPnP disable router
As an affiliate, we earn on qualifying purchases.
As an affiliate, we earn on qualifying purchases.
Key Questions
What devices are affected by CVE-2021-27137?
The vulnerability affects routers running DD-WRT firmware that has the vulnerable UPnP component enabled. Many consumer and small business routers using DD-WRT are potentially impacted.
How can I tell if my router is vulnerable?
Check your router’s firmware version and update to the latest release from the DD-WRT official site. If updates are unavailable, disable UPnP through your router’s settings to mitigate the risk.
Has a patch been officially released for this vulnerability?
It is unclear if a specific patch addressing CVE-2021-27137 has been widely released recently. Users should consult official DD-WRT advisories or update to the latest firmware version as recommended.
What are the potential consequences of exploitation?
Successful exploitation can lead to remote code execution, full control over the affected device, data theft, network compromise, or use of the device in botnet operations.
Source: kev
