Add vpatch-CVE-2026-42596 rule and test

.appsec-tests/vpatch-CVE-2026-42596/CVE-2026-42596.yaml

@@ -0,0 +1,25 @@
+## autogenerated on 2026-09-25 14:36:39
+id: CVE-2026-42596
+info:
+  name: CVE-2026-42596
+  author: crowdsec
+  severity: info
+  description: CVE-2026-42596 testing
+  tags: appsec-testing
+http:
+  - raw:
+      - |
+        POST /forms/libreoffice/convert HTTP/1.1
+        Host: {{Hostname}}
+        Content-Type: multipart/form-data; boundary=----testBoundary
+
+        ------testBoundary
+        Content-Disposition: form-data; name="downloadFrom"
+
+        [{"url":"http://[::ffff:127.0.0.1]:3000/health"}]
+        ------testBoundary--
+    cookie-reuse: true
+    matchers:
+      - type: status
+        status:
+          - 403

.appsec-tests/vpatch-CVE-2026-42596/config.yaml

@@ -0,0 +1,5 @@
+## autogenerated on 2026-09-25 14:36:39
+appsec-rules:
+  - ./appsec-rules/crowdsecurity/base-config.yaml
+  - ./appsec-rules/crowdsecurity/vpatch-CVE-2026-42596.yaml
+nuclei_template: CVE-2026-42596.yaml

appsec-rules/crowdsecurity/vpatch-CVE-2026-42596.md

@@ -0,0 +1,9 @@
+This rule provides virtual patching for **CVE-2026-42596**, an SSRF vulnerability in **Gotenberg**, published on 2026-05-14, with a CVSS 3.1 score of **9.4 (Critical)**.
+
+**Detection:** Detects IPv4-mapped IPv6 address SSRF attempts in Gotenberg downloadFrom requests.
+
+Virtual patching mitigates exploitation attempts, but it does not fix the underlying vulnerability: upgrading Gotenberg to a patched version is always recommended.
+
+### References
+- [CVE-2026-42596 on NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-42596)
+- [Exploit reference](https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-42596.yaml)

appsec-rules/crowdsecurity/vpatch-CVE-2026-42596.yaml

@@ -0,0 +1,35 @@
+## autogenerated on 2026-09-25 14:36:39
+name: crowdsecurity/vpatch-CVE-2026-42596
+description: 'Detects IPv4-mapped IPv6 address SSRF attempts in Gotenberg downloadFrom requests.'
+rules:
+  - and:
+      - zones:
+          - URI
+        transform:
+          - urldecode
+          - lowercase
+        match:
+          type: contains
+          value: '/forms/libreoffice/convert'
+      - zones:
+          - BODY_ARGS
+        variables:
+          - downloadFrom
+        transform:
+          - urldecode
+          - lowercase
+        match:
+          type: contains
+          value: '::ffff:'
+
+labels:
+  type: exploit
+  service: http
+  confidence: 3
+  spoofable: 0
+  behavior: 'http:exploit'
+  label: 'Gotenberg - SSRF'
+  classification:
+    - cve.CVE-2026-42596
+    - attack.T1190
+    - cwe.CWE-918

collections/crowdsecurity/appsec-virtual-patching.yaml

@@ -19,6 +19,7 @@ appsec-rules:
 - crowdsecurity/vpatch-CVE-2023-3519
 - crowdsecurity/vpatch-CVE-2023-42793
 - crowdsecurity/vpatch-CVE-2025-53693
+- crowdsecurity/vpatch-CVE-2026-42596
 - crowdsecurity/vpatch-CVE-2023-50164
 - crowdsecurity/vpatch-CVE-2023-38205
 - crowdsecurity/vpatch-CVE-2023-24489