Windows RPCSS svchost (-k RPCSS) Process Spawn Anomaly (Potential CVE-2022-26809)
Alerts on svchost.exe running RPCSS spawning anomalous child processes indicative of potential RPC abuse.
- Product
- windows
- Category
- process_creation
- Author
- Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
- Published
- 2022-04-13
- Updated
- 2026-07-31
ATT&CK techniques
Initial Access → ExecutionRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule flags Windows process creation events where svchost.exe running the RPCSS instance (ParentCommandLine contains "-k RPCSS") spawns a subprocess. This matters because RPC service anomalies can indicate attempted exploitation paths that result in unexpected child processes from a core Windows service host. It relies on process creation telemetry including the parent image and parent command line used to identify the RPCSS context.
Reporting behind it
- msrc.microsoft.comhttps://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-26809
- bleepingcomputer.comhttps://www.bleepingcomputer.com/startups/RpcSs.exe-14544.html
- twitter.comhttps://twitter.com/cyb3rops/status/1514217991034097664
- securonix.comhttps://www.securonix.com/blog/cve-2022-26809-remote-procedure-call-runtime-remote-code-execution-vulnerability-and-coverage/
- github.comhttps://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2022/Exploits/CVE-2022-26809/proc_creation_win_exploit_cve_2022_26809_rpcss_child_process_anomaly.yml
Changelog
v5- v5Candidate ingested via manual entry.2026-07-31
- v4Candidate ingested via manual entry.2026-07-31
- v3Candidate ingested via manual entry.2026-07-31
- v2Candidate ingested via manual entry.2026-07-31
- v1No changelog recorded for this version.2026-07-30
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
title: Windows RPCSS svchost (-k RPCSS) Process Spawn Anomaly (Potential CVE-2022-26809)
id: e0955686-32cd-45cf-8aa2-0a2d0f7daf56
status: test
description: This rule flags Windows process creation events where svchost.exe running the RPCSS instance (ParentCommandLine contains "-k RPCSS") spawns a subprocess. This matters because RPC service anomalies can indicate attempted exploitation paths that result in unexpected child processes from a core Windows service host. It relies on process creation telemetry including the parent image and parent command line used to identify the RPCSS context.
references:
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2022-26809
- https://www.bleepingcomputer.com/startups/RpcSs.exe-14544.html
- https://twitter.com/cyb3rops/status/1514217991034097664
- https://www.securonix.com/blog/cve-2022-26809-remote-procedure-call-runtime-remote-code-execution-vulnerability-and-coverage/
- https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2022/Exploits/CVE-2022-26809/proc_creation_win_exploit_cve_2022_26809_rpcss_child_process_anomaly.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2022-04-13
modified: 2023-02-03
tags:
- attack.initial-access
- attack.t1190
- attack.execution
- attack.t1569.002
- cve.2022-26809
- detection.emerging-threats
logsource:
category: process_creation
product: windows
detection:
selection:
ParentImage: C:\Windows\System32\svchost.exe
ParentCommandLine|contains: -k RPCSS
condition: selection
falsepositives:
- Unknown
- Some cases in which the service spawned a werfault.exe process
level: high
license: DRL-1.1
related:
- id: a7cd7306-df8b-4398-b711-6f3e4935cf16
type: derived