A 0-Day is a software vulnerability without an available fix, creating risk because defenders have limited time to mitigate exploitation.
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Background for this topic.
0-Day describes a software vulnerability unknown to the software maker or unpatched when first exploited. Attackers can use these flaws immediately, as no official fix or signature exists to block the exploit. Such vulnerabilities often affect widely deployed software or hardware, making them valuable for targeted attacks or widespread campaigns.
Because defenders lack patches or reliable detection signatures initially, they must rely on anomaly detection, network monitoring, and threat intelligence to identify suspicious activity linked to 0-day exploits. Rapid patching once a fix is released is critical to reduce exposure. Tracking emerging 0-day threats helps prioritize defensive measures and informs risk management decisions in environments where unpatched vulnerabilities pose significant security risks.
Ivanti has disclosed two critical vulnerabilities in Ivanti Endpoint Manager Mobile (EPMM), tracked as CVE-2026-1281 and CVE-2026-1340, that were exploited in zero-day attacks. [...]
Fortinet has confirmed a new, actively exploited critical FortiCloud single sign-on (SSO) authentication bypass vulnerability, tracked as CVE-2026-24858, and says it has mitigated the zero-day attacks by blocking FortiCloud SSO connections from devices running vulnerable firmware versions. [...]
Microsoft has released emergency security updates to patch a high-severity Office zero-day vulnerability exploited in attacks. [...]