Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows CVEs, Including Four Critical RCE Flaws in TCP/IP, IKEv2, Netlogon, and DNS

Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows (TL-2026-1184), also tracked as MDASH Windows RCE Batch, is a critical-severity software vulnerability scored CVSS 9.8, first published 2026-07-10. It has no confirmed attribution, affects Microsoft Windows TCP/IP Stack (tcpip.sys), references 4 CVEs (CVE-2026-33827, CVE-2026-33824, CVE-2026-41089), maps to 19 MITRE ATT&CK techniques (T1003, T1005, T1018), and is covered by 9 detection rules and 19 indicators of compromise.

Key facts for TL-2026-1184

Threat ID
TL-2026-1184
Also known as
MDASH Windows RCE Batch, MDASH 16 CVE Disclosure
Severity
CRITICAL
CVSS
9.8 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)
Status
PATCHED
Category
VULNERABILITY
First published
2026-07-10
Last reviewed
2026-07-10
Attribution confidence
LOW
Motivation
UNKNOWN
Target sectors
government administration, finance, health, technology, education, manufacturing, retail, energy, telecoms
Target regions
Global
Detection rules
9
Indicators of compromise
19

Malware and tooling in Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows

Malware and tooling: CyberGym benchmark, MDASH (Multi-Model Agentic Scanning Harness)

Microsoft's Multi-Model Agentic Scanning Harness (MDASH), a 100+ agent AI pipeline that discovers, debates, and proves Windows kernel/service vulnerabilities, surfaced 16 previously unknown CVEs across the April and May 2026 Patch Tuesdays, including four unauthenticated critical RCE flaws in tcpip.sys, ikeext.dll, netlogon.dll, and dnsapi.dll. The disclosures fed a record 200+ patched vulnerabilities in the June 2026 Patch Tuesday and preceded MDASH's transition into production across Windows, Azure, and identity engineering on June 17, 2026.

How Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows works

Microsoft's Security Response Center (MSRC) and Microsoft Research disclosed MDASH (Multi-Model Agentic Scanning Harness), an AI-driven vulnerability-discovery pipeline that orchestrates more than 100 specialized agents across an ensemble of frontier and distilled language models. MDASH runs a five-stage workflow: Prepare (builds language-aware code indices and threat models via commit analysis), Scan (auditor agents flag candidate vulnerabilities with supporting evidence), Validate (debater agents argue for and against exploitability and reachability), Dedupe (collapses semantically equivalent findings), and Prove (constructs and executes triggering inputs to confirm exploitability with a working proof-of-concept). The system uses a configurable model panel — a state-of-the-art model as the heavy reasoner, distilled models as cost-effective high-volume debaters, and a second independent SOTA model as a counterpoint — explicitly to avoid the blind spots of any single-model approach. Domain-specific plugins inject expertise the base models otherwise lack, such as Windows kernel calling conventions, lock invariants, and IPC trust boundaries.

Microsoft reported MDASH scored 88.45% on the CyberGym benchmark of 1,507 real-world vulnerabilities (the top score on the public leaderboard, ahead of Anthropic's Mythos Preview at 83.1% and OpenAI's GPT-5.5 at 81.8%), detected 21 of 21 planted vulnerabilities in an internal StorageDrive test with zero false positives, and demonstrated 96% historical recall against MSRC's known clfs.sys corpus (28 cases) and 100% recall against tcpip.sys (7 cases).

Applied against live Windows source, MDASH surfaced 16 previously unknown CVEs spanning the Windows networking and authentication stack — 10 kernel-mode and 6 user-mode vulnerabilities — the majority reachable from an unauthenticated network position. Four are rated CRITICAL remote code execution:

1. **CVE-2026-33827** (tcpip.sys, CVSS 3.1 8.1, CWE-362 Race Condition): an unsynchronized reference-count decrement in the Windows TCP/IP stack's handling of IPv4 packets carrying the Strict Source and Record Route (SSRR) option leads to a use-after-free. MDASH's own writeup notes the bug spans non-trivial control flow where 'the reference count might reach zero at the earlier release point,' a pattern difficult for single-model auditors lacking cross-file comparison. Published April 14, 2026. 2. **CVE-2026-33824** (ikeext.dll, CVSS 3.1 9.8, CWE-415 Double Free): an unauthenticated attacker who sends a crafted IKEv2 SA_INIT exchange with malformed fragmentation to a host with the IKE Extension service enabled (affecting RRAS VPN, DirectAccess, and Always-On VPN deployments) triggers a double-free spanning six source files; MDASH identified the flaw by contrasting the vulnerable path against a correctly implemented shallow-copy pattern elsewhere in the codebase. Published April 14, 2026. 3. **CVE-2026-41089** (netlogon.dll, CVSS 3.1 9.8, CWE-121 Stack-based Buffer Overflow): an unauthenticated CLDAP request with a crafted User= filter overflows a stack buffer in Netlogon, allowing remote code execution on a domain controller with no user interaction — assessed by researchers as wormable and the highest-urgency bug in the batch given that 'a compromised domain controller is a compromised domain.' Published May 12, 2026. 4. **CVE-2026-41096** (dnsapi.dll / Windows DNS Client, CVSS 3.1 9.8, CWE-122 Heap-based Buffer Overflow): a heap overflow triggered by a crafted UDP DNS response allows an attacker positioned to respond to DNS queries (rogue server or on-path/MitM) to achieve remote code execution on essentially any Windows host, since the DNS Client component runs on virtually every Windows machine. Published May 12, 2026.

The remaining 12 MDASH-discovered flaws are rated Important and span tcpip.sys, http.sys, ikeext.dll, and telnet.exe, covering denial-of-service, privilege-escalation, information-disclosure, and security-feature-bypass classes. All 16 CVEs were patched across Microsoft's April and May 2026 Patch Tuesday cycles. Microsoft framed the June 2026 record of 200+ patched vulnerabilities as partly attributable to MDASH's expanded scanning coverage, and moved MDASH from research project to production status on June 17, 2026, integrating it into Windows, Azure, and identity engineering workflows and extending Microsoft Defender integration to eligible enterprise customers in an expanded preview. No public evidence of in-the-wild exploitation of any of the four critical RCEs had been reported as of the reporting window; all four require only network reachability and no authentication or user interaction, making rapid patching the primary mitigation.

MITRE ATT&CK techniques used in TL-2026-1184

Credential Access

T1003 OS Credential Dumping; T1558 Steal or Forge Kerberos Tickets

Collection

T1005 Data from Local System

Discovery

T1018 Remote System Discovery; T1046 Network Service Discovery

Exfiltration

T1041 Exfiltration Over C2 Channel

Privilege Escalation

T1068 Exploitation for Privilege Escalation; T1078 Valid Accounts

Command and Control

T1071 Application Layer Protocol

Initial Access

T1190 Exploit Public-Facing Application

Execution

T1203 Exploitation for Client Execution

lateral-movement

T1210 Exploitation of Remote Services

Lateral Movement

T1210 Exploitation of Remote Services

Defense Evasion

T1211 Exploitation for Stealth

Impact

T1489 Service Stop; T1499 Endpoint Denial of Service

Resource Development

T1587 Develop Capabilities; T1588 Obtain Capabilities

Reconnaissance

T1592 Gather Victim Host Information; T1595 Active Scanning

Affected products and versions in Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows

  • Microsoft — Windows TCP/IP Stack (tcpip.sys)
    Vulnerable versions: Windows 10 1607; Windows 10 1809; Windows 10 21H2; Windows 10 22H2; Windows 11 22H3; Windows 11 23H2; Windows 11 24H2; Windows 11 25H2; Windows 11 26H1; Windows Server 2012
    Fixed in: April 2026 cumulative update per-build thresholds (e.g. Windows 10 1607 build 10.0.14393.9060+)
  • Microsoft — Windows IKE Extension Service (ikeext.dll)
    Vulnerable versions: Windows 10 1607; Windows 10 1809; Windows 10 21H2; Windows 10 22H2; Windows 11 23H2; Windows 11 24H2; Windows 11 25H2; Windows 11 26H1; Windows Server 2016 and later
    Fixed in: April 2026 cumulative update per-build thresholds
  • Microsoft — Windows Netlogon (netlogon.dll)
    Vulnerable versions: Windows Server 2012 before 6.2.9200.26079; Windows Server 2012 R2 before 6.3.9600.23181; Windows Server 2016 before 10.0.14393.9140; Windows Server 2019 before 10.0.17763.8755; Windows Server 2022 before 10.0.20348.5139; Windows Server 2022 23H2 before 10.0.25398.2330; Windows Server 2025 before 10.0.26100.32772
    Fixed in: May 2026 cumulative update, versions listed above and later
  • Microsoft — Windows DNS Client (dnsapi.dll)
    Vulnerable versions: Windows 11 23H2; Windows 11 24H2; Windows 11 25H2; Windows 11 26H1; Windows Server 2022 23H2; Windows Server 2025
    Fixed in: May 2026 cumulative update per-build thresholds

Remediation for Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows

Patches

  • April 2026 Patch Tuesday cumulative update (CVE-2026-33827, CVE-2026-33824)
  • May 2026 Patch Tuesday cumulative update (CVE-2026-41089, CVE-2026-41096)

Immediate actions

  • Apply the April 2026 Patch Tuesday updates addressing CVE-2026-33827 (tcpip.sys) and CVE-2026-33824 (ikeext.dll) on all affected Windows and Windows Server builds
  • Apply the May 2026 Patch Tuesday updates addressing CVE-2026-41089 (netlogon.dll) and CVE-2026-41096 (dnsapi.dll / DNS Client) with priority on domain controllers
  • Prioritize domain controllers for CVE-2026-41089 given wormable, unauthenticated, network-reachable exploitation and direct domain-compromise impact
  • Restrict inbound IKEv2/IPsec (UDP 500/4500) exposure to trusted networks where IKEEXT-dependent VPN services (RRAS, DirectAccess, Always-On VPN) are not required from the open internet
  • Filter or rate-limit inbound IPv4 packets carrying the Strict Source and Record Route (SSRR) option at network boundary devices as a compensating control for CVE-2026-33827
  • Ensure DNS Client traffic is not exposed to untrusted or on-path attackers; enforce DNS over trusted resolvers only to reduce CVE-2026-41096 exposure

Workarounds

  • Disable IKEv2/IKEEXT service on hosts that do not require VPN services until patched
  • Block SSRR-option IPv4 packets at perimeter firewalls/IDS as a temporary compensating control
  • Restrict domain controller CLDAP exposure to trusted management networks

Longer-term hardening

  • Deploy EDR/XDR with kernel-mode driver behavioral monitoring on tcpip.sys and ikeext.dll to catch exploitation attempts of unpatched or zero-day variants
  • Segment domain controllers from general network access and enforce strict CLDAP/LDAP monitoring for anomalous User= filter payloads
  • Adopt continuous vulnerability-scanning pipelines (AI-assisted or traditional fuzzing) for internet-facing Windows network-stack components
  • Track Microsoft Defender integration with MDASH threat intelligence as it expands from private preview to general availability

CVEs associated with Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows

CVE-2026-33827, CVE-2026-33824, CVE-2026-41089, CVE-2026-41096

Weaknesses (CWE) in Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows

CWE-362, CWE-415, CWE-121, CWE-122

Timeline of Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows

  • April 2026 Patch Tuesday ships fixes for CVE-2026-33827 (tcpip.sys race condition/UAF) and CVE-2026-33824 (ikeext.dll double-free), both later attributed to MDASH discovery.
  • Microsoft discloses MDASH's internal StorageDrive test detected 21 of 21 planted vulnerabilities with zero false positives, and historical recall testing showed 96% recall on MSRC's clfs.sys corpus (28 cases) and 100% recall on tcpip.sys (7 cases).
  • Microsoft discloses MDASH scored 88.45% on the CyberGym benchmark of 1,507 real-world vulnerabilities, topping the public leaderboard ahead of Anthropic's Mythos Preview (83.1%) and OpenAI's GPT-5.5 (81.8%).
  • Zero Day Initiative publishes its May 2026 Security Update Review, flagging CVE-2026-41089 (Netlogon) as the highest-urgency bug of the batch due to wormable, unauthenticated domain-controller compromise.
  • TheHackerNews, CSOonline, and other outlets report on the 16 MDASH-discovered Windows CVEs, detailing CVSS scores and affected components.
  • Microsoft Security Blog publishes 'Defense at AI speed,' revealing MDASH's architecture, CyberGym benchmark leadership (88.45%), and the 16-CVE Windows disclosure batch including the four critical RCEs.
  • May 2026 Patch Tuesday ships fixes for CVE-2026-41089 (netlogon.dll stack overflow) and CVE-2026-41096 (dnsapi.dll/DNS Client heap overflow).
  • June 2026 Patch Tuesday sets a company record of 200+ patched vulnerabilities, partly attributed to expanded MDASH scanning coverage feeding into the release.
  • MDASH transitions from research project to production status, integrating into Windows, Azure, and identity engineering workflows with expanded Microsoft Defender integration preview for eligible customers.

Sources cited for Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows

Threats related to Microsoft's MDASH AI Scanning Harness Uncovers 16 Windows

Detection coverage for TL-2026-1184

As of 2026-07-10, Threadlinqs Intelligence publishes 9 detection rule(s) for TL-2026-1184 across Splunk SPL, Microsoft KQL and Sigma, covering 19 indicator(s) of compromise. The whole corpus is readable without an account; a free account unlocks full detection query text in Splunk SPL, Microsoft KQL and Sigma; paid tiers add raw indicator values, correlation and the MCP server. Threadlinqs MCP server · View plans.

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