Also known as: Update Tuesday · monthly patch cycle
Patch Tuesday is the second Tuesday of each month, on which Microsoft and several other major vendors release their scheduled batch of security updates, giving administrators a predictable cadence for planning maintenance.
Predictable release timing lets organisations plan testing and deployment windows in advance rather than reacting to unscheduled releases. That predictability is the entire point, and it works well for the routine majority of fixes.
The trade-off is that batching creates a known window of exposure. Attackers reverse-engineer released patches to build exploits for systems that have not yet updated — a pattern informally called Exploit Wednesday. Vulnerabilities under active exploitation are released out-of-band rather than held for the schedule.
A vulnerability disclosed and patched on the second Tuesday of the month may see working exploits circulating within days, targeting the many organisations whose maintenance window has not yet arrived.
N-Day
An n-day is a vulnerability that has already been publicly disclosed and patched, but remains exploitable on systems that have not yet applied the update.
Zero-Day
A zero-day is a software vulnerability that attackers know about and exploit before the vendor has released a patch, leaving defenders zero days to prepare a fix.
Vulnerability Management
Vulnerability management is the ongoing process of identifying, prioritising, remediating, and verifying fixes for security weaknesses across an organisation's systems and software.
KEV Catalog
The KEV (Known Exploited Vulnerabilities) catalog is a list maintained by the US Cybersecurity and Infrastructure Security Agency of vulnerabilities with confirmed evidence of active exploitation in the wild.
Exploit
An exploit is code or a technique that takes advantage of a specific vulnerability to cause unintended behaviour, such as executing attacker-supplied code, bypassing authentication, or crashing a service.