Exploit.

An exploit is the practical realization of a vulnerability — the recipe that turns a theoretical bug into a working attack. It may be a short script, a malicious document, a crafted network packet, or a complex multi-stage chain.

Anatomy and classification

Exploits are classified by purpose (remote code execution, local privilege escalation, denial of service, information leak), by target (kernel, browser, IoT firmware, web application) and by maturity (proof-of-concept, functional, weaponized, in-the-wild). A memory-corruption exploit typically pairs a primitive that hijacks control flow with a payload — often shellcode or a Return-Oriented-Programming (ROP) chain assembled from existing code. Because reliable single-bug exploitation is now rare on hardened targets, attackers build exploit chains: for example a browser renderer bug leaking memory to defeat ASLR, followed by a sandbox escape and a kernel privilege escalation.

Real examples

EternalBlue (CVE-2017-0144) exploited an SMBv1 flaw and drove the 2017 WannaCry and NotPetya outbreaks. Log4Shell (CVE-2021-44228, CVSS 10.0), disclosed December 2021, let an unauthenticated attacker trigger remote code execution simply by getting a vulnerable Log4j instance to log an attacker-controlled ${jndi:...} string — one of the most widely exploited bugs ever.

Mitigations and defensive use

Exploit mitigations — DEP/NX, ASLR, stack canaries, CFG/CET, and pointer authentication — raise the cost of turning a bug into code execution. Defenders study public exploits and databases such as Exploit-DB and Metasploit to validate patches, simulate attacks via penetration testing, write detection signatures, and prioritise remediation (CISA's Known Exploited Vulnerabilities catalog flags what is being used in the wild).

flowchart LR
  A[Vulnerability<br/>e.g. buffer overflow] --> B[Trigger<br/>crafted input]
  B --> C[Control primitive<br/>overwrite return addr / pointer]
  C --> D[Defeat mitigations<br/>info-leak beats ASLR]
  D --> E[Payload executes<br/>shellcode / ROP chain]
  E --> F[Objective<br/>RCE · priv-esc · data theft]
  D -.->|next stage| G[Sandbox escape /<br/>kernel exploit]
  G --> F