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[Home](/)[Glossary](/glossary)Zero-Day Vulnerability[Back to Glossary](/glossary)Zero-Day Vulnerability
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A previously unknown security flaw that has no available patch, giving defenders zero days to prepare before it can be exploited.

security conceptthreat intelligencerisk management

A zero-day vulnerability is a software security flaw that is unknown to the software vendor and for which no patch or mitigation exists. The term "zero-day" refers to the fact that developers have had zero days to address the vulnerability since its discovery. Zero-day exploits are highly valuable to attackers because there are no signatures or patches to defend against them.

Zero-day vulnerabilities are discovered through various means: independent security research, bug bounty programs, state-sponsored cyber operations, and criminal hacking. The market for zero-day exploits is substantial, with government agencies and private companies paying significant sums for undisclosed vulnerabilities.

While zero-day vulnerabilities cannot be prevented through patching alone, defense-in-depth strategies — including network segmentation, least privilege access, behavioral detection, and continuous monitoring — can limit their impact.

How APVISO tests for this: While APVISO cannot discover zero-days in underlying software, its AI-driven approach excels at finding novel application-specific vulnerabilities that traditional signature-based scanners would miss. By reasoning about application logic rather than matching known patterns, APVISO identifies unique security issues specific to your codebase.

Related Terms
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[CVE (Common Vulnerabilities and Exposures)](/glossary/cve)[Patch Management](/glossary/patch-management)[Attack Surface](/glossary/attack-surface)

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