Description

Integer overflow or wraparound in Windows Installer allows an authorized attacker to elevate privileges locally.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-11T17:18:06.730Z",
  "pubdate": "2026-08-11T17:18:06.730Z",
  "executiveSummary": "An integer overflow or wraparound vulnerability exists within Windows Installer, affecting the Windows operating system environment. This vulnerability allows an authorized local attacker to execute arbitrary code and achieve local privilege escalation. The flaw arises during arithmetic calculations within the installation subsystem, where improper bounds or overflow checks permit values to wrap around, leading to memory corruption or unsafe pointer manipulation. Successful exploitation grants the adversary elevated system-level permissions, bypassing standard security boundaries and access controls on the target machine. Exploitation requires local access to the system and that the attacker possesses authorization to initiate or interact with installation processes. The risk implication is severe, as a low-privileged user can leverage this vulnerability to gain complete administrative control over the affected operating system, enabling full compromise of confidentiality, integrity, and availability. Because the attack vector is strictly local, remote exploitation is precluded, but insider threats or compromised user accounts present a significant vector for leveraging this flaw.",
  "technicalDetails": "The root cause of the vulnerability resides in an integer overflow or wraparound condition within the Windows Installer component. Specifically, when the installer parses crafted installation packages, patches, or internal data structures, arithmetic operations calculating buffer sizes or memory allocations fail to account for integer boundaries. When input values are manipulated to exceed the maximum representable value for the integer type, the value wraps around to a small integer or zero. This discrepancy between the calculated size and the actual memory allocated results in heap-based buffer overflows or out-of-bounds write conditions when the application subsequently attempts to write data into the undersized buffer.\nThe vulnerable component is the core Windows Installer service or its associated dynamic link libraries responsible for handling installation transactions and package validation. The affected versions encompass standard implementations of Windows Installer present in vulnerable Windows operating system configurations. Authentication requirements dictate that the attacker must already possess local access to the target host and valid credentials to initiate execution flows within the context of the installer subsystem. Privilege requirements are limited to standard, unprivileged local user accounts, as the goal of the exploit is privilege escalation.\nThe step-by-step attack flow begins with the local attacker authenticating to the target Windows system with low privileges. The adversary crafts or supplies a malicious installation package or interacts with the Windows Installer Application Programming Interfaces in a manner that triggers the vulnerable arithmetic operation. As the installer processes the input, the integer overflow occurs during the allocation sizing phase. The system allocates a memory buffer that is significantly smaller than required by the payload data. Subsequent copy or write operations overflow the heap buffer, allowing the attacker to corrupt adjacent memory structures. Through precise heap manipulation and control over the corrupted pointers, the attacker achieves arbitrary code execution within the context of a privileged system service or the local SYSTEM account, successfully escalating privileges locally and completing the post-exploitation phase with full administrative capabilities."
}