CVE-2026-107782 winsiderss CVE debrief

Who should care

Defenders responsible for System Informer installations should assess exposure and prioritize patching to prevent exploitation. This includes reviewing and applying the patch (version 4.0.26241.138), inventorying System Informer installations, and monitoring for suspicious activity related to SiSvcApiPort. Security teams should also review compensating controls for exposed systems and track exceptions and remediation efforts.

Why it matters

Defenders should prioritize verifying and applying the patch (version 4.0.26241.138) to prevent exploitation of the incorrect authorization vulnerability in System Informer before 4.0.26241.138.

• Local attackers can execute code as SYSTEM
• Privileged APIs can be accessed from any Authenticode-signed process
• Patching is required to prevent exploitation

Technical summary

The phsvc helper in System Informer before 4.0.26241.138 contains an incorrect authorization vulnerability. This allows local attackers to reach privileged APIs by connecting from any Authenticode-signed process. The vulnerability is due to inadequate authorization checks in the phsvc helper, enabling attackers to access sensitive APIs. Defenders should prioritize verifying and applying the patch (version 4.0.26241.138) to prevent exploitation. The patch fixes the authorization issue, preventing attackers from executing code as SYSTEM.

Defensive priority

Defenders should prioritize verifying and applying the patch (version 4.0.26241.138) to prevent exploitation.

Recommended defensive actions

• Verify and apply the patch (version 4.0.26241.138) to prevent exploitation
• Inventory System Informer installations to identify potential exposure
• Monitor for suspicious activity related to SiSvcApiPort
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The vulnerability exists in System Informer before 4.0.26241.138, allowing local attackers to execute code as SYSTEM by connecting to SiSvcApiPort and calling PhSvcApiCreateService. This is possible because the phsvc helper does not properly validate connections from Authenticode-signed processes. Defenders should verify and apply the patch (version 4.0.26241.138) to prevent exploitation and monitor for suspicious activity related to SiSvcApiPort.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.