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.
Microsoft patched a high-severity Windows Kernel privilege escalation vulnerability in February, six months after being informed that the flaw was being exploited as a zero-day. [...]
Microsoft Fixed Bug in February That Gave Kernel-Level Access to North Korean APTNorth Korea's Lazarus hackers exploited a Windows AppLocker driver zero-day to gain kernel-level access and turn off security tools that could detect the group's bring-your-own-vulnerable-driver exploitation techniques. Microsoft fixed the bug in its February patch dump.
The notorious Lazarus Group actors exploited a recently patched privilege escalation flaw in the Windows Kernel as a zero-day to obtain kernel-level access and disable security software on compromised hosts
UNC5325 Can Remain in Hacked Devices Despite Factory Reset and PatchesChinese threat actors are continuing to persist after exploiting the recent Ivanti Connect Secure VPN vulnerability even after factory resets, system upgrades and patches. The threat actor, UNC5325, is adept at "living off the land" techniques, warned threat intelligence firm Mandiant.
North Korean threat actors known as the Lazarus Group exploited a flaw in the Windows AppLocker driver (appid.sys) as a zero-day to gain kernel-level access and turn off security tools, allowing them to bypass noisy BYOVD (Bring Your Own Vulnerable Driver) techniques. [...]
Group-IB research warns of rising use of zero-day threats in targeted attacks