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Detection rules › Sigma

Cisco ASA Exploitation Activity - Proxy

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

Detects suspicious requests to Cisco ASA WebVpn via proxy logs associated with CVE-2025-20333 and CVE-2025-20362 exploitation.

MITRE ATT&CK coverage

TacticTechniques
Initial AccessT1190 Exploit Public-Facing Application

Rule body yaml

title: Cisco ASA Exploitation Activity - Proxy
id: 15697955-6a29-47ca-92e9-0e05efae3260
status: experimental
description: |
    Detects suspicious requests to Cisco ASA WebVpn via proxy logs associated with CVE-2025-20333 and CVE-2025-20362 exploitation.
references:
    - https://x.com/defusedcyber/status/1971492272966598683
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-11-20
tags:
    - attack.initial-access
    - attack.t1190
    - cve.2025-20333
    - cve.2025-20362
    - detection.emerging-threats
logsource:
    category: proxy
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem:
            - '/+CSCOU+/MacTunnelStart.jar'
            - '/+CSCOL+/csvrloader64.cab'
            - '/+CSCOL+/csvrloader.jar'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    cs-method: 'GET'
    cs-uri-stem:
        - '/+CSCOU+/MacTunnelStart.jar'
        - '/+CSCOL+/csvrloader64.cab'
        - '/+CSCOL+/csvrloader.jar'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
cs-methodeq
  • GET
cs-uri-stemeq
  • /+CSCOL+/csvrloader.jar
  • /+CSCOL+/csvrloader64.cab
  • /+CSCOU+/MacTunnelStart.jar