CVE-2026-69391

CVE-2026-69391 is a stack-based buffer overflow (CWE-121) in the Microsoft Windows Broker Infrastructure Service, the Windows component that manages brokered background and inter-process operations. Because the attack vector is local, requires only low privileges, and needs no user interaction, an attacker who can already execute limited code on a Windows machine can trigger the flaw via crafted requests to the service. Successful exploitation allows the attacker to elevate privileges locally to higher (typically SYSTEM-level) rights, with high impact on confidentiality, integrity, and availability (CVSS 3.1 score of 7.8). Any Windows system where the Broker Infrastructure Service is present is affected; the exact affected Windows version ranges were not specified in the available data and should be taken from Microsoft's advisory. Exploitation status is currently quiet: there is no public proof-of-concept, the flaw is not in CISA KEV, and an EPSS of 0.3% (25th percentile) suggests low probability of near-term exploitation.

What to do: Patch via Windows Update (or WSUS/your endpoint management tooling) as soon as Microsoft's update for CVE-2026-69391 is available, and check Microsoft's advisory for the definitive list of affected Windows versions. Prioritize hosts where untrusted or low-privileged users can run code, such as workstations, terminal/RDS servers, and VDI, since the flaw requires only local low-privilege access. Until patched, restrict local code execution by unprivileged users on sensitive hosts and monitor the Broker Infrastructure Service for anomalous behavior.