Security researchers have issued a warning regarding the active exploitation of a critical vulnerability by the Gafgyt botnet, targeting end-of-life Zyxel P660HN-T1A routers. This specific vulnerability, identified as CVE-2017-18368 with a high CVSS v3 score of 9.8, revolves around a command injection flaw within the Remote System Log forwarding function.
This flaw, accessible to unauthenticated users, resides in the ViewLog.asp page and can be exploited through the remote_host parameter. Devices utilizing firmware versions 126.96.36.199 v001/3.40(ULM.0)b31 or older are at risk.
Although Zyxel had addressed this vulnerability in 2017 through the release of new firmware, the Gafgyt botnet’s persistence in exploiting this flaw, as indicated by Fortinet’s outbreak alert, remains a concerning issue. The alert, dated August 7, 2023, reports a significant surge in attacks on the vulnerability, with Fortinet’s observation of an average of 7,300 exploit attempts per day since July 2023.
In response to the heightened risk, the US Cybersecurity and Infrastructure Security Agency (CISA) has included the vulnerability in its Known Exploited Vulnerabilities Catalog and has mandated federal agencies to address this flaw by August 28, 2023. In light of this threat, Zyxel released an advisory, acknowledging the listing on the CISA catalog but clarifying that a patch had been provided for the customized P660HN-T1A router in 2017.
Furthermore, the advisory notes that the P660HN-T1A running the latest generic firmware, version 3.40(BYF.11), is not susceptible to CVE-2017-18368. However, given the router’s end-of-life status, users are strongly advised to replace it with a newer-generation product to ensure optimal protection.