Cybersecurity headlines often focus on zero‑day exploits, those mysterious vulnerabilities that attackers discover before vendors even know they exist. But the reality inside most enterprises is that n‑day exploits, the attacks on already disclosed and patched vulnerabilities, are far more dangerous. They thrive in the gap between disclosure and patch adoption. When you add insider threats to the mix, the risk multiplies. Insiders know patch cycles, they understand which systems lag behind, and they can weaponize both zero‑days and n‑days to devastating effect.
In 2025, Microsoft faced criticism for not immediately patching CVE‑2025‑9491, a zero‑day in how Windows handles shortcut (.lnk) files. Attackers embedded malicious payloads inside shortcuts and delivered them through spearphishing emails themed around NATO workshops and EU Commission meetings. Victims who clicked the file triggered malware like PlugX RAT and Ursnif. Groups such as Mustang Panda and other state‑aligned actors were behind the campaigns (Unit42, 2025).
For insiders, the angle is clear. Shortcut files are common in daily workflows. An insider could plant malicious .lnk files on shared drives or internal email threads, bypassing perimeter defenses. Because Microsoft delayed a patch, enterprises were left exposed, and insiders had a ready‑made tool to escalate privileges or exfiltrate data.
Another case was CVE‑2025‑59287, a critical bug in Windows Server Update Services (WSUS). Attackers exploited a serialization flaw to push arbitrary code across fleets of servers. Proof‑of‑concept code appeared quickly, and exploitation began in October 2025 before Microsoft issued an emergency out‑of‑band fix (Huntress, 2025).
For insiders, WSUS is a dream weapon. Admins with console access could abuse the flaw to mass‑deploy malicious payloads across enterprise endpoints. Because WSUS runs with high privileges, exploitation turns trusted infrastructure into a backdoor. This is a textbook example of how insider access combined with n‑day exploitation magnifies risk.
Unit 42 also reported “Landfall,” a zero‑click spyware campaign exploiting CVE‑2025‑21042 in Samsung Galaxy devices. Attackers embedded malicious loaders in DNG image files, enabling remote code execution and SELinux policy manipulation. The spyware recorded calls, messages, files, and location data, and it was observed in Iraq, Iran, Turkey, and Morocco (Unit42, 2025).
The insider threat angle is subtle but powerful. In enterprises with bring your own device policies, personal Galaxy phones become surveillance footholds. Insiders carrying compromised devices can unknowingly or deliberately leak sensitive corporate data. Because the exploit bypassed mobile defenses and cleaned up artifacts, detection was minimal.
Google patched CVE‑2025‑2783, a Chrome sandbox bypass exploited by surveillance vendors and clusters tied to “Mem3nt0 Mori.” Attackers delivered spyware through malicious links, enabling session hijacking and credential theft (Google, 2025).
For insiders, browsers are the new perimeter. Compromised Chrome sessions allow takeover of SaaS accounts like email and storage. Unsanctioned extensions expand the attack surface. An insider could exploit this flaw to silently persist inside corporate environments, blending malicious activity with routine work.
Sophos disclosed CVE‑2025‑61932, a zero‑day in Motex Lanscope, a popular endpoint manager in Japan. The flaw allowed unauthenticated requests and arbitrary code execution. Researchers found hundreds of exposed servers online. Motex patched the issue, but exploitation was already underway (Sophos, 2025).
For insiders, endpoint managers are superweapons. With console access, they can mass deploy payloads, disable defenses, or exfiltrate data. Because Lanscope runs with system level privileges, exploitation converts administrative trust into organization wide compromise.
Not all insider exploitation is technical. In 2025, a former executive at L3Harris Trenchant pleaded guilty to stealing and selling zero‑day exploit components intended for Five Eyes customers to a Russian broker. The theft caused tens of millions in losses and highlighted how insiders can divert exploit tooling itself (DOJ, 2025).
This case shows that insider threats are not limited to using exploits. They can also steal and resell them, undermining supply chain integrity and spreading capabilities beyond intended controls.
While zero‑days grab headlines, most breaches stem from n‑day exploitation. The average time to weaponize a disclosed vulnerability has collapsed to about five days. Enterprises often take weeks or months to patch due to testing and downtime. Once proof of concept code is public, it is quickly integrated into exploit kits. Insiders know these cycles and can exploit lagging systems before IT teams catch up.
The lesson is clear. Zero‑days show attacker sophistication, but n‑days show defender failure. Insiders thrive in that failure window. They know which systems are unpatched, which tools run with high privileges, and how to blend malicious activity with routine work. Insider threat programs must account not just for malicious intent but also for negligent patch management. Governance, monitoring, and rapid patch adoption are as critical as technical defenses.
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