Windows Application Logs: Detect WSUS deserialization exploitation via InvalidCastException indicators

Flags WSUS (EventID 7053) application log errors matching invalid cast/object data provider strings indicative of CVE-2025-59287 exploitation.

FreeReviewedSigma · High · v5

Product: windows
Service: application
Author: Swachchhanda Shrawan Poudel (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2025-10-31
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Initial Access → Execution

Recon
Resource Dev
Initial Access
- T1190Exploit Public-Facing Application
Execution
- T1203Exploitation for Client Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule identifies exploitation attempts against Windows Server Update Services by matching specific deserialization-related cast exception strings in WSUS application logs. Attackers may exploit this class of issues to trigger harmful object deserialization behavior, so these error patterns can serve as high-signal indicators. It relies on Windows application log events with EventID 7053 where Provider_Name is Windows Server Update Services and the event message contains the listed InvalidCastException and related object-casting text.

Reporting behind it

Related detections9 linkedT1190 — drag to rearrange

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Windows Application Logs: Detect WSUS deserialization exploitation via InvalidCastException indicators

Pivot detection · T1190 · 9 related

Changelog

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No 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.

windows-application-logs-wsus-deserialization-exploitation-indicators-for-cve-20-e5f66e87

title: "Windows Application Logs: Detect WSUS deserialization exploitation via InvalidCastException indicators"
id: dd6db5a9-299b-479d-8366-535a230220f2
status: experimental
description: This rule identifies exploitation attempts against Windows Server Update Services by matching specific deserialization-related cast exception strings in WSUS application logs. Attackers may exploit this class of issues to trigger harmful object deserialization behavior, so these error patterns can serve as high-signal indicators. It relies on Windows application log events with EventID 7053 where Provider_Name is Windows Server Update Services and the event message contains the listed InvalidCastException and related object-casting text.
references:
  - https://unit42.paloaltonetworks.com/cve-2025-59287/
  - https://hawktrace.com/blog/CVE-2025-59287-UNAUTH
  - https://github.com/0xBruno/WSUSploit.NET/tree/e239bce9d6b5f46a346e1e4c4d5e0a2a20d5c639
  - https://www.huntress.com/blog/exploitation-of-windows-server-update-services-remote-code-execution-vulnerability
  - https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2025/Exploits/CVE-2025-59287/win_wsus_exploit_cve_2025_59287.yml
author: Swachchhanda Shrawan Poudel (Nextron Systems), Huntrule Team
date: 2025-10-31
tags:
  - attack.execution
  - attack.initial-access
  - attack.t1190
  - attack.t1203
  - cve.2025-59287
  - detection.emerging-threats
logsource:
  product: windows
  service: application
detection:
  selection:
    Provider_Name: Windows Server Update Services
    EventID: 7053
    Data|contains|all:
      - System.InvalidCastException
      - System.Windows.Data.ObjectDataProvider
      - Unable to cast object of type
      - System.Windows.Media.Brush
  condition: selection
falsepositives:
  - Legitimate WSUS operations that may trigger similar error messages
level: high
license: DRL-1.1
related:
  - id: e5f66e87-7d6b-404f-92fe-7aa67814b5cd
    type: derived

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