An arbitrary function call is an exploit primitive that lets an attacker redirect execution to a function of their choice, often with attacker-controlled arguments. It usually comes from control-flow corruption and can be used to reach sensitive routines, bypass checks, or pivot into further code execution.
How Arbitrary Function Calls Work
An arbitrary function call means the attacker has steered execution into a chosen function, usually by corrupting a return address, function pointer, vtable entry, or similar control data. The primitive matters because it turns a memory-safety bug into a controllable execution step, often before the final payload is even reached.
This is more specific than generic code execution. The key question is not only whether control flow is broken, but whether the attacker can direct that control toward a function that already exists in the process, which may be enough to disable protections, leak secrets, or trigger further exploitation.
Why Arbitrary Function Calls Are Dangerous
A chosen function call can be dangerous even when the attacker cannot inject shellcode. If the target function performs file access, process creation, memory writes, network activity, or privilege-related operations, the attacker may be able to repurpose legitimate program logic for hostile ends. In practice, the danger often comes from the function's side effects, not from the call itself.
This primitive also helps bridge partial compromise into deeper control. A constrained redirect may be enough to call a sequence of routines that relax checks, expose memory, or set up a more reliable exploit path. In that sense, an arbitrary function call is often a stepping stone inside a larger exploit chain rather than the final objective.
Common Causes and Prerequisites
Arbitrary function calls usually depend on memory corruption, especially overwrite conditions that affect a control-flow target. Classic causes include buffer overflows, heap corruption, use-after-free, type confusion, and pointer misuse. The attacker needs not only a write primitive, but also knowledge of how the program stores and later dereferences the target pointer or dispatch table.
Whether the exploit succeeds often depends on platform hardening and code layout. Indirect branch protections, address randomization, control-flow integrity, and modern compiler defenses can all raise the difficulty, but none of them eliminate the underlying risk if the application still exposes a reachable and useful call target.
How Defenders Think About It
Defenders treat arbitrary function calls as evidence of a broken trust boundary inside the process. The practical response is to understand which control data can be influenced, which functions are reachable, and what those functions can do once invoked. That analysis helps distinguish a noisy crash from a real exploit primitive.
For incident response, the important follow-up is to review whether the function call exposed memory, altered authorization state, or opened a path to further execution. If exploitation is suspected, the vulnerable process should be treated as compromised until the control-flow path and any downstream effects have been reviewed.
Standards & Framework Alignment
This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.
MITRE ATT&CK addresses the attack and risk surface, while NIST SP 800-53 Rev 5, CIS Controls v8 and OWASP ASVS set the governance and control requirements practitioners need to meet.
| Framework | Control / Reference | Relevance |
|---|---|---|
| MITRE ATT&CK | T1055 — Process Injection | Arbitrary function calls often support attacker code execution and control-flow manipulation. |
| Recommendation — Map the control-flow abuse to T1055 and hunt for execution redirection and post-exploitation activity. | ||
| NIST SP 800-53 Rev 5 | SI-10 — Information Input Validation | Input validation limits attacker-controlled data that can corrupt function pointers or call targets. |
| SI-7 — Software, Firmware, and Information Integrity | Integrity controls help detect tampering that enables hostile function redirection or payload staging. | |
| Recommendation — Apply SI-10 to reduce unsafe inputs that can drive control-flow corruption. Use SI-7 to detect tampering that precedes or follows control-flow abuse. | ||
| CIS Controls v8 | CIS-4 — Secure Configuration of Enterprise Assets and Software | Hardening reduces exploitability of memory-corruption paths that lead to arbitrary calls. |
| CIS-16 — Application Software Security | Application security practices directly address bugs that enable arbitrary function calls. | |
| Recommendation — Harden exposed software paths under CIS-4 to reduce exploitability of memory corruption. Use CIS-16 to find and fix memory-safety defects that enable hostile control flow. | ||
| OWASP ASVS | V15 — Secure Coding and Architecture | ASVS secure design and coding guidance addresses the root causes of exploitable control-flow corruption. |
| V16 — Security Logging and Error Handling | Logging and error handling help detect anomalous crashes and exploit attempts around control-flow abuse. | |
| Recommendation — Apply V15 to prevent unsafe memory handling that can turn into arbitrary function calls. Use V16 to log abnormal failures that may indicate exploit development or abuse. | ||
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Reviewed and updated by the NHIMG editorial team on November 2, 2026.
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