Unauthenticated Stack Buffer Overflow RCE in Windows DNS (CVE-2026-62878)
CVSS 3.1
9.8critical
EPSS
1%p68
Published
()
Modified
AI analysis
Windows DNS contains a stack-based buffer overflow (CWE-121) that an unauthenticated, network-adjacent or internet-reachable attacker can trigger by sending crafted input to the DNS service. Successful exploitation yields remote code execution on the target host, with high impact on confidentiality, integrity and availability (CVSS 3.1: 9.8). The flaw affects the DNS component shipped with Windows 10 1607 and 1809 and with Windows Server 2012, 2016, 2019, 2022 and 2025; systems running the DNS Server role, especially internet-facing DNS servers and domain controllers, are the primary targets. Microsoft, which assigned the CVE, has issued a fix, and the flaw appeared amid a record-sized run of Patch Tuesday releases. No in-the-wild exploitation is currently known: it is not in CISA's KEV, no public proof-of-concept is available, and EPSS estimates only a 1.3% probability of exploitation within 30 days.
What to do: Apply Microsoft's security update addressing CVE-2026-62878 on all affected Windows 10 (1607, 1809) and Windows Server (2012-2025) hosts, prioritizing internet-facing DNS servers and domain controllers. Until patched, restrict exposure of TCP/UDP 53 to trusted clients and forwarders and avoid publishing Windows DNS directly to the internet. Verify which hosts expose port 53 at the perimeter and monitor for anomalous DNS request patterns as a stopgap detection.
Affected
microsoft Windows 10
1607
microsoft Windows 10
1809
microsoft Windows Server
2012
microsoft Windows Server
2016
microsoft Windows Server
2019
microsoft Windows Server
2022
microsoft Windows Server
2025
Estimated exposure
masshundreds of thousands of internet-exposed Windows DNS endpoints, plus millions of DNS Server role instances in enterprise/Active Directory deployments — The DNS Server role is effectively ubiquitous on Windows Server and domain controllers, and recurring public internet-wide scans of port 53 typically find on the order of hundreds of thousands of Microsoft DNS endpoints exposed, while the…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
Description
Stack-based buffer overflow in Windows DNS allows an unauthorized attacker to execute code over a network.
Microsoft's August 2026 Patch Tuesday fixes 398 CVEs, including an actively exploited WinSock zero-day CVE-2026-68820 and wormable DNS RCE CVE-2026-62878.
Microsoft's August 2026 Patch Tuesday addresses 398 CVEs across Windows, Office, Azure, Exchange Server, SharePoint, Teams, .NET and other products, with 62 rated Critical. The actively exploited CVE-2026-68820 is a use-after-free in the Windows WinSock afd.sys driver that can yield SYSTEM privileges via a race condition. CVE-2026-62878 is a critical, wormable stack buffer overflow in Windows DNS Server allowing unauthenticated, remote code execution without user interaction. Other notable fixes include WDS TFTP RCE CVE-2026-62893, a QUIC flaw affecting roughly 13.5 million sites (CVE-2026-62815), an Exchange authentication bypass EoP demonstrated at Pwn2Own Berlin (CVE-2026-62911), and two TPM 2.0 reference implementation fixes.
Microsoft's August 2026 Patch Tuesday fixes 400+ vulnerabilities, including an actively exploited Windows zero-day (CVE-2026-68820) used by North Korean attackers.
Microsoft's August 2026 Patch Tuesday fixes over 400 vulnerabilities, including CVE-2026-68820, a use-after-free in the Windows Ancillary Function Driver exploited in the wild by North Korean actors deploying a kernel-mode rootkit in Operation Dream Job. Critical unauthenticated remote code execution flaws in Microsoft QUIC (CVE-2026-62815) and Windows DNS (CVE-2026-62878) were also patched, alongside a SharePoint RCE chain combining CVE-2026-63520 with CVE-2026-55040. Researcher Nightmare-Eclipse released ShieldBreak, a PoC bypassing the July RoguePlanet Microsoft Defender patch (CVE-2026-50656), confirmed working by Will Dormann on Windows 11.
Microsoft's August Patch Tuesday fixes 398 CVEs, including actively exploited Windows zero-day CVE-2026-68820 used by Lazarus for SYSTEM privilege escalation.
Microsoft's August 2026 Patch Tuesday release addresses 398 new vulnerabilities, 62 rated Critical by the Zero Day Initiative, with CVE-2026-68820 (CVSS 7.0), a use-after-free in the afd.sys Windows kernel driver, the only flaw flagged as actively exploited. Check Point Research attributed exploitation of the privilege escalation bug to Lazarus' Operation Dream Job campaign. Four unauthenticated remote code execution flaws rated 9.8 affect Windows DNS Server (CVE-2026-62878, called wormable by ZDI), Windows Deployment Services (CVE-2026-62893), Microsoft QUIC (CVE-2026-62815) and HPC Pack (CVE-2026-59124). The release also completes a two-part SharePoint fix with RCE component CVE-2026-63520, following July's authentication bypass fix CVE-2026-55040.
Microsoft's September 2026 Patch Tuesday fixes a record 974 CVEs, including two actively exploited Windows zero-days, CVE-2026-85880 and CVE-2026-81963.
Microsoft fixed a record 974 CVEs in its September 2026 Patch Tuesday, surpassing the previous record of 570 in July 2026, with Windows affected by 723 flaws and Office by 111, including 119 critical vulnerabilities. Two zero-days are actively exploited: CVE-2026-85880, a 7.8 heap-based buffer overflow in Windows ALPC allowing AppContainer privilege escalation, and CVE-2026-81963, an improper link resolution flaw in the Windows Update Stack enabling local privilege escalation. Microsoft attributed the update surge partly to agentic AI tools used to discover zero-day vulnerabilities, and researchers highlighted critical RCE flaws in Windows DNS, DHCP and Deployment Services as priorities.