Potential Java WebShell Upload in SAP NetViewer Server

Status: experimental
Severity: high
Log source: category webserver
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects potential Java webshell uploads via HTTP requests with Content-Type 'application/octet-stream' and Java file extensions. This behavior might indicate exploitation of vulnerabilities like CVE-2025-31324, which allows remote code execution through webshells in SAP NetViewer.

Known false positives

Legitimate uploads of Java files in development environments

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1505.003` Server Software Component: Web Shell

Rule body

title: Potential Java WebShell Upload in SAP NetViewer Server
id: 639b893f-f93a-4e53-a7c8-f08cf73fe7f7
status: experimental
description: |
    Detects potential Java webshell uploads via HTTP requests with Content-Type 'application/octet-stream' and Java file extensions.
    This behavior might indicate exploitation of vulnerabilities like CVE-2025-31324, which allows remote code execution through webshells in SAP NetViewer.
references:
    - https://blog.eclecticiq.com/china-nexus-nation-state-actors-exploit-sap-netweaver-cve-2025-31324-to-target-critical-infrastructures
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-05-14
tags:
    - attack.persistence
    - attack.t1505.003
    - detection.emerging-threats
    - cve.2025-31324
logsource:
    category: webserver
detection:
    selection:
        cs-content-type: 'application/octet-stream'
        cs-method: 'POST'
        cs-uri-stem|contains|all:
            - '/irj/'
            - '.jsp'
        cs-uri-stem|endswith:
            - '.class'
            - '.java'
            - '.jsp'
    condition: selection
falsepositives:
    - Legitimate uploads of Java files in development environments
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    cs-content-type: 'application/octet-stream'
    cs-method: 'POST'
    cs-uri-stem|contains|all:
        - '/irj/'
        - '.jsp'
    cs-uri-stem|endswith:
        - '.class'
        - '.java'
        - '.jsp'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`cs-content-type`	eq	`application/octet-stream`	`field:"cs-content-type" kind:eq value:"application/octet-stream"`
`cs-method`	eq	`POST`	`field:"cs-method" kind:eq value:"POST"`
`cs-uri-stem`	ends_with	`.class` `.java` `.jsp`	`field:"cs-uri-stem" kind:ends_with`
`cs-uri-stem`	match	`.jsp` `/irj/`	`field:"cs-uri-stem" kind:match`