SafeBreach researchers Or Yair and Shahak Morag have uncovered a significant flaw in the Windows LDAP client code, which they’ve dubbed Win-DDoS. This novel attack technique can turn public domain controllers (DCs) into a powerful botnet for launching distributed denial-of-service (DDoS) attacks. The researchers presented their findings at the DEF CON 33 security conference. The technique is particularly concerning because it allows attackers to leverage existing Windows infrastructure without needing to breach devices or purchase their own resources, making the attacks difficult to trace.
Win-DDoS works by exploiting how DCs handle Lightweight Directory Access Protocol (LDAP) referrals. An attacker sends an initial remote procedure call (RPC) to a DC, causing it to become a CLDAP client. The DC then queries the attacker’s server, which responds with a referral list containing numerous URLs that all point to a single target. The DC, following the referral chain, repeatedly sends LDAP queries to the victim server. This flood of traffic, multiplied by thousands of DCs, can easily overwhelm the target and cause a denial of service. The attack essentially turns the Windows platform itself into both the victim and the weapon.
What makes Win-DDoS so effective is its ability to generate high-bandwidth attacks without requiring an attacker to buy dedicated infrastructure. This bypasses the usual financial and logistical hurdles of setting up a large-scale botnet. Furthermore, since the attacker isn’t directly compromising devices, the technique is stealthy and leaves a minimal footprint, making attribution extremely challenging. The attack’s unique methodology, which uses the referral process to redirect traffic, allows it to bypass traditional security measures designed to detect compromised endpoints.
The research also highlighted other related denial-of-service (DoS) vulnerabilities within the Windows ecosystem. The flawed LDAP referral process, for example, can be manipulated to trigger an LSASS crash, a system reboot, or even a blue screen of death (BSoD) by sending excessively long referral lists. Additionally, the researchers identified a DoS technique called TorpeDoS, which allows a single computer to generate an RPC-call-rate equivalent to that of a full DDoS attack. SafeBreach also found several other DoS flaws (CVE-2025-26673, CVE-2025-32724, CVE-2025-49716, and CVE-2025-49722) that can crash domain controllers, some without requiring authentication.
The implications of these findings are significant. They challenge the long-held assumption that internal systems are safe from abuse unless fully compromised. The zero-click, unauthenticated nature of some of these vulnerabilities means that attackers can remotely crash systems if they are publicly accessible, and even with minimal internal network access, they can achieve the same results against private infrastructure. This forces a re-evaluation of enterprise threat models, risk assessment strategies, and defense mechanisms to account for these previously overlooked blind spots in the Windows platform.
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