Security Affairs newsletter Round 479 by Pierluigi Paganini

CVE-2021-40444 is a remote code execution vulnerability in the Microsoft MSHTML browser rendering engine, which Microsoft Office documents can load on Windows systems. It is triggered when a user is convinced to open a specially crafted Office document containing a malicious ActiveX control hosted by the MSHTML engine (tracked as a path-traversal-class issue, CWE-22). A successful attacker gains the ability to run arbitrary code in the context of the logged-on user, with greater impact when that user has administrative rights. Any Windows system that can open Office documents is exposed, spanning Windows 7, 8.1, RT 8.1, Windows 10 (1507 through 21H1) and Windows Server 2004/2008. Exploitation is confirmed in the wild: Microsoft observed targeted attacks at disclosure, the flaw is in CISA's KEV with known ransomware use, and Microsoft released security updates on September 14, 2021.

Do: Apply Microsoft's security updates released September 14, 2021 for your Windows version immediately; this is a CISA KEV item with known ransomware use, so patching is treated as mandatory. As interim protection, keep Microsoft Defender Antivirus/Defender for Endpoint signatures current (enterprise detection build 1.349.22.0 or newer, with alerts appearing as 'Suspicious Cpl File Execution') and avoid opening untrusted Office documents, since exploitation requires user interaction with a crafted file.

D-Link DIR-859 routers running firmware 1.06B01 contain a critical path traversal flaw (CWE-22, CVSS 9.8) in the HTTP POST request handler of /hedwig.cgi. An unauthenticated remote attacker can manipulate the 'service' parameter with a directory-traversal path (e.g., ../../../../htdocs/webinc/getcfg/DHCPS6.BRIDGE-1.xml) to access files outside the intended location. Given the critical rating with high confidentiality, integrity, and availability impacts, successful exploitation can expose sensitive router configuration (potentially including credentials) and lead to full device compromise. Only DIR-859 units still in service are affected: D-Link has confirmed the product is end-of-life, so no patched firmware is available. Exploitation is now in the wild — CISA added the flaw to its Known Exploited Vulnerabilities catalog on 2025-06-25, EPSS puts 30-day exploitation probability at 82.7%, a public proof-of-concept exists, and news reports indicate threat actors are actively exploiting D-Link DIR-series flaws.

Do: Because the DIR-859 is end-of-life, there is no firmware fix — replace the router with a currently supported model, as the vendor recommends. If replacement is not immediate, minimize exposure by disabling remote/WAN management access to the device and any port-forwarding or UPnP rules that expose the web interface, and monitor for exploitation attempts against /hedwig.cgi. Federal agencies must follow CISA BOD 22-01 and remediate by the assigned KEV due date.

CVE-2024-20399 is a command injection flaw (CWE-78) in the CLI of Cisco NX-OS Software, caused by insufficient validation of arguments passed to specific configuration CLI commands. An authenticated attacker who already holds Administrator credentials can trigger it by submitting crafted input as the argument of an affected configuration command, gaining the ability to execute arbitrary commands as root on the device's underlying operating system. Because Administrator access is required, the flaw is effectively a privilege-escalation issue following credential compromise, and it grants no additional privilege on Nexus 3000 Series, Nexus 7000 Series running NX-OS 8.1(1) or later, and Nexus 9000 Series in standalone NX-OS mode, which already allow administrative bash-shell access to the OS. Any organization running affected NX-OS on Cisco Nexus switching is in scope, with the practical risk concentrated in environments where admin credentials may have been stolen. Exploitation has been observed in the wild: the China-linked group 'Velvet Ant' (associated with Salt Typhoon) used it as a zero-day to compromise U.S. ISPs and telecom providers, and CISA added it to the Known Exploited Vulnerabilities catalog on 2024-07-02.

Do: Upgrade affected Nexus switches to a fixed NX-OS release per Cisco's security advisory, as required by the CISA KEV listing (apply mitigations per vendor instructions or discontinue use if fixes are unavailable). Restrict and audit Administrator-level CLI access on NX-OS devices, and hunt for suspicious configuration-command activity or unexplained root-level actions, given Velvet Ant/Salt Typhoon targeting of telecom and ISP networks. For Nexus 3000, Nexus 7000 (8.1(1)+), and Nexus 9000 standalone-mode devices the flaw adds no privilege, but patching is still recommended.

Rejetto HTTP File Server (HFS), a free Windows-based file-sharing server, contains a template injection vulnerability (CWE-94/CWE-1336) in versions up to and including 2.3m that allows a remote, unauthenticated attacker to execute arbitrary commands by sending a specially crafted HTTP request. The flaw is network-exploitable with no privileges or user interaction required (CVSS 3.1: 9.8 Critical), and the affected 2.3m release is no longer supported by the vendor. Any system running Rejetto HFS 2.3m or earlier is affected, with instances exposed directly to the internet at the greatest risk. Exploitation is confirmed in the wild: CISA added the vulnerability to the Known Exploited Vulnerabilities catalog on 2024-07-09 with known ransomware use, EPSS assigns a 99.5% probability of exploitation within 30 days, and public PoCs and a Metasploit module are available. Related reporting on Russia-aligned TAG-110 activity (HATVIBE/CHERRYSPY malware) against Ukrainian institutions highlights active targeting around the same period.

Do: Because HFS 2.3m is end-of-life with no fixed 2.x version indicated in the available data, follow CISA's required action: apply mitigations per vendor instructions or discontinue use of the product, and at minimum remove it from direct internet exposure (firewall/ACL rules or VPN-only access). Hunt for compromise by checking HFS access logs for crafted HTTP requests containing template/macro syntax and the HFS service process for unexpected child processes. Organizations subject to CISA KEV remediation deadlines should prioritize this fix given the 9.8 Critical severity, 99.5% EPSS, and known ransomware use.