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.
Fortinet has silently patched a critical zero-day vulnerability in its FortiWeb web application firewall, which is now being widely exploited. [...]
Cybercrime crew has ravaged multiple private organizations using Oracle EBS zero-day for months The UK's National Health Service (NHS) is investigating claims of a cyberattack by extortion crew Clop.…
British Health System Investigates Claim Amid Wave of Enterprise Data TheftsRansomware gang Clop has claimed the United Kingdom's National Health Service among its latest victims. The NHS confirmed that it is listed on a cybercriminal group's dark website, but did not comment on Clop's claims. The hack attack appears tied to Oracle E-Business Suite exploits.
Flaw Enabled Remote Code Execution, Say AWS ResearchersResearchers from AWS said they spotted a hacking campaign taking advantage of a zero-day vulnerability in Cisco network access control software before the routing giant patched it earlier this year. The flaw let attackers perform pre-authentication remote code execution.
The same APT hammered critical bugs in Citrix NetScaler (CVE-2025-5777) and the Cisco Identity Service Engine (CVE-2025-20337) in a sign of growing adversary interest in identity and access management systems.
Vendors (still) keep mum An "advanced" attacker exploited CitrixBleed 2 and a max-severity Cisco Identity Services Engine (ISE) bug as zero-days to deploy custom malware, according to Amazon Chief Information Security Officer CJ Moses.…
Amazon's threat intelligence team on Wednesday disclosed that it observed an advanced threat actor exploiting two then-zero-day security flaws in Cisco Identity Service Engine (ISE) and Citrix NetScaler ADC products as part of attacks designed to deliver custom malware
An advanced threat actor exploited the critical vulnerabilities "Citrix Bleed 2" (CVE-2025-5777) in NetScaler ADC and Gateway, and CVE-2025-20337 affecting Cisco Identity Service Engine (ISE) as zero-days to deploy custom malware. [...]
Microsoft on Tuesday released patches for 63 new security vulnerabilities identified in its software, including one that has come under active exploitation in the wild
Microsoft has patched a zero-day vulnerability in the Windows Kernel under active exploitation by threat actors
Security teams may have a less burdensome rollout in November after October's Goliath Patch Tuesday, but shouldn't wait on a few top-priority fixes.
Today is Microsoft's November 2025 Patch Tuesday, which includes security updates for 63 flaws, including one actively exploited zero-day vulnerability. [...]
CISA has demanded federal agencies patch a zero-day vulnerability affecting Samsung devices used in LandFall spyware attacks
CISA ordered U.S. federal agencies today to patch a critical Samsung vulnerability that has been exploited in zero-day attacks to deploy LandFall spyware on devices running WhatsApp. [...]