CISA Warns of Zimbra, SharePoint Flaw Exploits; Cisco Zero-Day Hit in Ransomware Attacks

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has urged government agencies to apply patches for two security flaws impacting Synacor Zimbra Collaboration Suite (ZCS) and Microsoft Office SharePoint, stating they have been actively exploited in the wild.

The vulnerabilities in question are as follows –

• CVE-2025-66376 (CVSS score: 7.2) – A stored cross-site scripting vulnerability in the Classic UI of ZCS, where attackers could abuse Cascading Style Sheets (CSS) @import directives in an HTML e-mail message. (Fixed in versions 10.0.18 and 10.1.13 in November 2025)
• CVE-2026-20963 (CVSS score: 8.8) – A deserialization of untrusted data vulnerability in Microsoft Office SharePoint that allows an unauthorized attacker to execute code over a network. (Fixed in January 2026)

There are currently no public reports referencing the exploitation of aforementioned flaws, who may be exploiting them, and the scale of such efforts. In light of active exploitation, Federal Civilian Executive Branch (FCEB) agencies are recommended to apply patches for CVE-2025-66376 by April 1, 2026, and for CVE-2026-20963 by March 23, 2026.

The disclosure comes as Amazon revealed that threat actors associated with Interlock ransomware have exploited a maximum-severity security flaw impacting Cisco’s firewall management software (CVE-2026-20131, CVSS score: 10.0) since January 26, 2026, more than a month before it was publicly disclosed.

“Interlock has historically targeted specific sectors where operational disruption creates maximum pressure for payment,” Amazon said. These sectors include education, engineering, architecture, construction, manufacturing, industrial, health care, and government entities.

The attack once again highlights a persistent pattern of threat actors targeting edge network devices from different vendors, including Cisco, Fortinet, Ivanti, and others, to obtain initial access to target networks. The fact that CVE-2026-20131 was weaponized as a zero-day shows that attackers are investing time and resources to find previously unknown flaws that could grant them elevated access.