CVE-2026-50496

What it actually does

This vulnerability is an out-of-bounds read reachable over the network through the Windows Network Policy Server SNMP functionality. An unauthenticated remote attacker can send specially crafted SNMP traffic to an affected Windows system running the vulnerable service path and trigger unsafe memory access. Based on the CVSS vector, the primary assessed impact is service availability degradation or crash rather than code execution; the description also indicates potential information disclosure from unintended memory reads.

Why it matters to the business

Organizations running affected Windows client or server versions with Network Policy Server and SNMP functionality exposed may experience disruption to network authentication, policy, or monitoring services if the vulnerable component is crashed remotely. If SNMP is reachable from untrusted networks, attackers could cause outages without credentials or user interaction. Although this is not currently listed in CISA KEV and no public exploit maturity is reported, it affects many supported Windows versions, so patching should be prioritized for internet-facing, perimeter, RADIUS/NPS, and infrastructure monitoring systems.

How an attack unfolds

An attacker first identifies Windows systems exposing SNMP, typically UDP/161, and determines whether Network Policy Server-related SNMP functionality is enabled. The attacker then sends a malformed SNMP request designed to trigger an out-of-bounds read in the vulnerable code path. Because exploitation requires no authentication and no user interaction, any reachable vulnerable service may be targeted directly over the network. Successful exploitation can cause the service or hosting process to fault, potentially disrupting NPS/SNMP functionality and, depending on memory exposure behavior, may disclose limited process memory contents. Repeated attempts may appear as recurring SNMP service crashes, NPS interruptions, or application fault events following inbound SNMP traffic.

How to fix it

Apply the relevant Microsoft security updates for the affected Windows versions as soon as they are available through Windows Update, WSUS, Microsoft Update Catalog, or enterprise patch management. Because no fixed version list was provided, treat the vendor security update for CVE-2026-50496 and later cumulative updates as the authoritative remediation baseline. If immediate patching is not possible, restrict SNMP access to trusted management hosts only, block UDP/161 and UDP/162 from untrusted networks, disable SNMP where it is not required, and avoid exposing Network Policy Server management interfaces to the internet. Review NPS/SNMP configurations and remove legacy or unused SNMP communities, especially default or broadly shared community strings.

How to confirm the fix worked

Confirm that affected Windows systems have installed the Microsoft security update or a later cumulative update that includes the fix. Validate with enterprise patch inventory, Windows Update history, WSUS/SCCM/Intune compliance data, or PowerShell checks such as Get-HotFix compared against Microsoft’s advisory for the applicable OS build. Confirm that SNMP is disabled where unnecessary or reachable only from approved monitoring subnets. Use network scans to verify that UDP/161 is not exposed to untrusted networks. On servers where NPS/SNMP must remain enabled, perform controlled validation from an approved scanner and confirm that malformed or unexpected SNMP traffic no longer causes SNMP, NPS, or related service crashes.

Typical attack path

1. Scan networks for Windows hosts exposing SNMP, especially UDP/161.
2. Identify servers likely running Network Policy Server, RADIUS, or infrastructure monitoring integrations.
3. Send specially crafted SNMP packets to the vulnerable service.
4. Trigger an out-of-bounds read in the Windows Network Policy Server SNMP component.
5. Cause service instability, denial of service, or possible unintended memory disclosure.
6. Repeat requests to sustain disruption or probe for leaked information.

How to detect it

Review network, endpoint, and Windows event logs for signs of suspicious SNMP activity followed by service instability. Key sources include firewall logs, IDS/IPS telemetry, NetFlow, Windows System logs, Windows Application logs, Service Control Manager events, Windows Error Reporting, and NPS/IAS logs if enabled. Look for inbound UDP/161 traffic from unusual external or internal sources, bursts of malformed or failed SNMP requests, and repeated crashes or restarts of SNMP, NPS, IAS, or their hosting processes. Correlate timestamps between inbound SNMP traffic and Event ID 7031/7034 service termination events, Application Error Event ID 1000 process faults, or Windows Error Reporting Event ID 1001 crash reports. Because no public exploit pattern is provided, detection should focus on behavioral evidence: unexpected SNMP exposure, high-volume or malformed SNMP probes, and service crashes shortly after SNMP traffic.

• UDP/161
• UDP/162
• SNMP Service
• The SNMP Service service terminated unexpectedly
• The SNMP Service service entered the stopped state
• Network Policy Server
• The Network Policy Server service terminated unexpectedly
• IAS
• The IAS service terminated unexpectedly
• snmp.exe
• %SystemRoot%\System32\snmp.exe
• Faulting application name: snmp.exe
• Application Error
• Windows Error Reporting
• Event ID 7031
• Event ID 7034
• Event ID 1000
• Event ID 1001

What your security team should do

• Prioritize patching Windows servers running Network Policy Server, RADIUS, SNMP, or network infrastructure monitoring roles.
• Immediately block inbound SNMP traffic from the internet and from untrusted internal segments.
• Inventory all affected Windows 10, Windows 11, and Windows Server systems listed in the advisory and identify which have SNMP or NPS roles enabled.
• Disable SNMP on systems where it is not operationally required.
• Restrict SNMP to dedicated monitoring hosts using host firewall rules, network ACLs, or management VLANs.
• Review logs for prior SNMP/NPS crashes, especially repeated Service Control Manager and Application Error events after inbound UDP/161 traffic.
• Monitor for scanning and malformed SNMP traffic targeting Windows infrastructure systems.
• Track Microsoft guidance for the exact cumulative update or KB applicable to each OS version.