CVE-2026-21509 is a vulnerability tracked across 14 threat clusters and 35 intelligence report mentions on ThreatCluster. First observed January 26, 2026; most recent activity March 26, 2026.
Microsoft Office 2016 to 2024 and Office 365 apps are affected by a zero-day vulnerability (CVE-2026-21509) that is currently being exploited in attacks. Microsoft has released emergency security updates to address this…
OpenSSL has patched a high-severity stack buffer overflow vulnerability, tracked as CVE-2025-15467. This flaw allows unauthenticated attackers to trigger denial-of-service conditions and potentially execute remote code…
Russian cyber group APT28, also known as Fancy Bear, has been exploiting vulnerabilities in TP-Link and MikroTik routers to conduct large-scale DNS hijacking operations. This campaign, which has affected over 18,000…
APT28, a Russia-linked advanced persistent threat group, conducted a cyberespionage campaign named Operation MacroMaze from September 2025 to January 2026. The campaign involved deploying macro malware embedded in…
ESET researchers have identified the resurgence of the Sednit group, a notorious Russian cybercriminal organization, linked to the deployment of a keylogger named SlimAgent in Ukraine. This activity is traced back to a…
CERT-UA has reported a new wave of cyberattacks targeting Ukrainian government agencies and EU organizations, exploiting the Microsoft Office vulnerability CVE-2026-21509. Attackers are using malicious emails disguised…
A critical vulnerability (CVE-2026-21509) in Microsoft Office has been identified, allowing attackers to exploit the application's reliance on untrusted inputs for security decisions. This flaw enables the bypassing of…
Microsoft has issued an emergency patch for a vulnerability, CVE-2026-21509, affecting Microsoft 365 Apps for Enterprise and Office 2019 and 2016. The flaw is currently being exploited in phishing attacks targeting…
Cyberattacks in the UK increased by 129% last year, with the NCSC managing four major incidents weekly. Concurrently, Microsoft issued emergency updates for a high severity vulnerability (CVE-2026-21509) in Office…
Fortinet has confirmed that attackers are actively exploiting a vulnerability in FortiCloud's single sign-on (SSO) authentication, affecting even fully patched devices. The exploitation allows unauthorized access, with…