Add vpatch-CVE-2021-25281 rule and test (#1630)

* Add vpatch-CVE-2021-25281 rule

* Add vpatch-CVE-2021-25281 test config

* Add CVE-2021-25281.yaml test

* Add vpatch-CVE-2021-25281 rule to vpatch collection

---------

Co-authored-by: Thibault "bui" Koechlin <thibault@crowdsec.net>

Author: crowdsec-automation

.appsec-tests/vpatch-CVE-2021-25281/CVE-2021-25281.yaml

@@ -0,0 +1,21 @@
+## autogenerated on 2026-01-07 15:07:56
+id: CVE-2021-25281
+info:
+  name: CVE-2021-25281
+  author: crowdsec
+  severity: info
+  description: CVE-2021-25281 testing
+  tags: appsec-testing
+http:
+  - raw:
+      - |
+        POST /run HTTP/1.1
+        Host: {{Hostname}}
+        Content-Type: application/json
+
+        {"client":"wheel_async","fun":"pillar_roots.write","data":"testing","path":"../../../../../../../tmp/testing","username":"1","password":"1","eauth":"pam"}
+    cookie-reuse: true
+    matchers:
+    - type: status
+      status:
+       - 403

.appsec-tests/vpatch-CVE-2021-25281/config.yaml

@@ -0,0 +1,5 @@
+## autogenerated on 2026-01-07 15:07:56
+appsec-rules:
+  - ./appsec-rules/crowdsecurity/base-config.yaml
+  - ./appsec-rules/crowdsecurity/vpatch-CVE-2021-25281.yaml
+nuclei_template: CVE-2021-25281.yaml

appsec-rules/crowdsecurity/vpatch-CVE-2021-25281.yaml

@@ -0,0 +1,33 @@
+## autogenerated on 2026-01-07 15:07:56
+name: crowdsecurity/vpatch-CVE-2021-25281
+description: 'Detects SaltStack Salt API authentication bypass via wheel_async client in /run endpoint.'
+rules:
+  - and:
+      - zones:
+          - URI
+        transform:
+          - lowercase
+        match:
+          type: equals
+          value: /run
+      - zones:
+          - BODY_ARGS
+        variables:
+          - json.client
+        transform:
+          - lowercase
+        match:
+          type: equals
+          value: wheel_async
+
+labels:
+  type: exploit
+  service: http
+  confidence: 3
+  spoofable: 0
+  behavior: 'http:exploit'
+  label: 'SaltStack Salt - Auth Bypass'
+  classification:
+    - cve.CVE-2021-25281
+    - attack.T1190
+    - cwe.CWE-287

collections/crowdsecurity/appsec-virtual-patching.yaml

@@ -148,6 +148,7 @@ appsec-rules:
 - crowdsecurity/vpatch-CVE-2025-13315
 - crowdsecurity/vpatch-CVE-2025-52970
 - crowdsecurity/vpatch-CVE-2025-47188
+- crowdsecurity/vpatch-CVE-2021-25281
 - crowdsecurity/vpatch-CVE-2025-55749
 - crowdsecurity/vpatch-CVE-2024-2862
 author: crowdsecurity