What is zero-day?
A zero-day attack is a type of cyber attack that exploits a previously unknown vulnerability in a computer system or application.
Azərbaycanca: Zero-day hücumu əvvəllər bilinməyən və hələ də patchlənməmiş zəifliklərdən istifadə edən hücum növüdür.
How it works
Zero-day attacks work by taking advantage of security gaps that have not yet been discovered or patched by the vendor. These types of attacks are particularly dangerous because organizations and users have not had time to protect themselves.
Defense checklist5
- 01
Apply security updates and patches in a timely manner
- 02
Regularly scan and monitor networks and systems
- 03
Implement multi-factor authentication (MFA)
- 04
Update and improve security policies and procedures
- 05
Conduct regular testing to verify the effectiveness of security measures
Real-world evidence
Russian threat group 'Laundry Bear' exploited a Zimbra zero-day to target US and Ukraine. Similarly, zero-day vulnerabilities were exploited in Check Point SmartConsole and SonicWall SMA.
Sources
- Russian Hackers Exploit Zimbra Zero-Day Against US, Ukraine Targetsdarkreading
- Russian Espionage Group Exploited Zimbra Zero-Day to Steal Mail and 2FA Codeshackernews
- Check Point warns of SmartConsole zero-day exploited in attacksbleepingcomputer
- CVE-2026-16355: JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed invd
- ⚡ Weekly Recap: WordPress RCE, SonicWall 0-Days, AI Service Attacks, SharePoint 0-Day and Morehackernews
- Inc Ransomware Exploits SonicWall SMA Zero-Daysdarkreading
- Three Steps to the Terminal: A Siemens ROX II Zero-Day Trilogyunit42
- Records Are Made to Be Broken: Patch Tuesday Raises Triage Stakesdarkreading
- Smashing Security podcast #472: AI gets hacked, and BitLocker gets bypassedgrahamcluley
- Zero-Day Exploitation of Vulnerability (CVE-2026-20245) in Cisco Catalyst SD-WAN Managercisa_kev
- This month in security with Tony Anscombe – May 2026 editionwelivesecurity
- Russian espionage group using novel Zimbra exploit to steal sensitive data from Western countriescyberscoop
Other attack types
See also6
This guide is AI-written from the real incident sources skopnix collected — the examples above are drawn from those cited items, nothing is invented.