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.
Weekly headline count for the current query.
The researcher known as "Nightmare-Eclipse" published a proof-of-concept (PoC) exploit for the Windows Defender vulnerability in early June after dropping several other Microsoft zero-days.
After gaining a foothold in thousands of Fortinet firewalls, the attackers are starting to monetize that access, and are also piling on a Nextcloud zero-day bug.
A major bug in Oracle's ERP software disproportionately affected American universities, and hackers have capitalized by stealing gobs of data.
A newly discovered, critical zero-day vulnerability is under attack; a Qilin ransomware affiliate has been blamed for at least one incident.
After a disgruntled security researcher published several zero-day exploits in recent weeks, Microsoft seemingly indicated criminal charges were in order.
YellowKey, GreenPlasma, and MiniPlasma add to the growing list of vulnerabilities a security researcher disclosed over the past six weeks.
CVE-2026-42897 stems from a cross-site scripting (XSS) vulnerability and can allow an attacker to compromise Outlook Web Access (OWA) mailboxes.
It's the first time in two years with no zero-days. But with 137 flaws to patch, including nine critical ones, admins still have plenty of work to do.
Shortly after the authentication-bypass flaw was disclosed multiple proof-of-concept exploits appeared, and one researcher claims there's been zero-day activity for at least a month.
An attacker has been using maliciously crafted PDF files to exploit a zero-day in Adobe Acrobat and Reader for at least four months.
Under the alias 'Chaotic Eclipse,' a researcher released a PoC exploit for a zero-day flaw that allows for system takeover by a local user, citing an undisclosed beef with Microsoft.
Microsoft says the financially motivated cybercrime group has exploited n-day and zero-day vulnerabilities in campaigns predicated on speed.
The authentication bypass flaw, tracked as CVE-2026-35616, is the latest in a series of Fortinet vulnerabilities that have been exploited in the wild.
A sophisticated iOS exploit chain leverages multiple zero-day vulnerabilities and is targeting users in Saudi Arabia, Turkey, Malaysia, and Ukraine.
The exploitation activity against CVE-2026-21385, a high-severity memory corruption flaw, could be tied to commercial spyware or nation-state threat groups.
The maximum-severity vulnerability CVE-2026-20127 was exploited by an unknown but sophisticated threat actor who left very little evidence behind.
After detecting a zero-day attack, the country's effective response was attributed to the tight relationship between its government and private industry.
It's time to phase out the "patch and pray" approach, eliminate needless public interfaces, and enforce authentication controls, one expert says.
To stop the ongoing attacks, the cybersecurity vendor took the drastic step of temporarily disabling FortiCloud single sign-on (SSO) authentication for all devices.
To exploit the vulnerability, an attacker would need either system access or be able to convince a user to open a malicious Office file.