EUVD-2026-56744
GHSA-cwvp-6g58-w4q7
Severity by source
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Description confirms DoS only; independently assigning C:N/I:N despite vendor's C:H/I:H - heap overflow via network with no auth, high complexity gating.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
7DescriptionCVE.org
Heap-based buffer overflow in Windows iSCSI Target Service allows an unauthorized attacker to deny service over a network.
AnalysisAI
Heap-based buffer overflow in the Windows iSCSI Target Service enables an unauthenticated remote attacker to trigger denial of service across a wide range of Windows Server versions from 2012 through 2025. The vendor-assigned CVSS vector of C:H/I:H/A:H suggests potential impact beyond the description's stated denial-of-service scope, warranting attention to whether memory corruption could extend to confidentiality or integrity compromise. No public exploit or active exploitation has been identified at time of analysis; however, SSVC designates the attack as automatable, elevating the urgency for organizations running exposed iSCSI targets to apply available patches.
Technical ContextAI
The iSCSI Target Service is a Windows Server role that allows a Windows system to present block storage devices over a TCP/IP network using the iSCSI protocol (typically TCP port 3260). The root cause is CWE-122, a heap-based buffer overflow, which arises when network-supplied iSCSI protocol data exceeds the bounds of a heap-allocated buffer without adequate validation or bounds checking. This class of flaw can corrupt heap metadata, adjacent objects, or control structures, enabling an attacker to cause service crashes or, in severe cases, influence program control flow. The affected scope spans Windows Server 2012 through 2025 and Windows 10 versions 1607 and 1809, indicating the vulnerable code path exists in a shared or long-lived implementation of the service across over a decade of Windows releases.
RemediationAI
Apply the Microsoft-released security updates addressing this vulnerability immediately, available via Windows Update or the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-65796. Target fixed builds are: 10.0.14393.9418 for Windows Server 2016 and Windows 10 1607; 10.0.17763.9115 for Windows Server 2019 and Windows 10 1809; 10.0.20348.5499 for Windows Server 2022; 10.0.26100.33296 for Windows Server 2025; 6.3.9600.23337 for Windows Server 2012 R2; and 6.2.9200.26279 for Windows Server 2012. As a compensating control on systems where immediate patching is not feasible, restrict inbound network access to TCP port 3260 (iSCSI) via host-based firewall or perimeter controls to only authorized iSCSI initiator IP addresses - note this reduces exposure but does not eliminate the vulnerability and may disrupt legitimate storage operations if not carefully scoped. On servers not intentionally serving as iSCSI targets, disabling the iSCSI Target Service role entirely removes the attack surface with no operational impact.
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Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Buffer Overflow
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External POC / Exploit Code
Leaving vuln.today