Linux Binary Launched Process with Null Argv

name: Linux Binary Launched Process with Null Argv
id: 0085652a-e682-45a2-a40c-5bb68b8f260e
version: 2
creation_date: '2026-05-12'
modification_date: '2026-07-17'
author: Raven Tait, Splunk
status: production
type: TTP
description: |-
    The following analytic detects kernel-level events where a setuid binary launches a shell or interpreter with a NULL argument vector, which occurs when a privilege escalation exploit gains root and executes a process via execve() without constructing a legitimate argument array.
data_source:
    - Linux Messages Syslog
search: |
    `linux_syslog` "NULL argv" "empty string added"
    | rex field=_raw "process '(?<launching_process>[^']+)' launched '(?<launched_process>[^']+)' with NULL argv"
    | where isnotnull(launching_process) AND isnotnull(launched_process)
    | stats
        count                        AS occurrences,
        min(_time)                   AS firstTime,
        max(_time)                   AS lastTime,
        values(_raw)                 AS message,
        values(host)                 AS dest
        by host, launching_process, launched_process
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | table dest, launching_process, launched_process,
            firstTime, lastTime, occurrences, message
    | `linux_binary_launched_process_with_null_argv_filter`
how_to_implement: To successfully implement this search, you need to have relevant kernel logs ingested with the Splunk Add-On for Unix and Linux (https://splunkbase.splunk.com/app/833).
known_false_positives: Legitimate false positives are rare but can occur when custom or poorly written setuid binaries, PAM modules, or login frameworks invoke shells programmatically without constructing a proper argv array. However, mainstream setuid binaries like su, sudo, and pkexec on modern Linux distributions always pass arguments, so any hit involving those specific processes should be treated as high confidence.
references:
    - https://www.elastic.co/security-labs/copy-fail-dirtyfrag-linux-page-bugs-in-the-wild
drilldown_searches:
    - name: View the detection results for - "$dest$"
      search: '%original_detection_search% | search  dest = "$dest$"'
      earliest_offset: $info_min_time$
      latest_offset: $info_max_time$
    - name: View risk events for the last 7 days for - "$dest$"
      search: '| from datamodel Risk.All_Risk | search normalized_risk_object IN ("$dest$") | stats count min(_time) as firstTime max(_time) as lastTime values(search_name) as "Search Name" values(risk_message) as "Risk Message" values(analyticstories) as "Analytic Stories" values(annotations._all) as "Annotations" values(annotations.mitre_attack.mitre_tactic) as "ATT&CK Tactics" by normalized_risk_object | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`'
      earliest_offset: 7d
      latest_offset: "0"
finding:
    title: Binary spawned process with NULL argv on $dest$ indicating possible privilege escalation.
    entity:
        field: dest
        type: system
        score: 50
analytic_story:
    - Linux Privilege Escalation
asset_type: Endpoint
cve:
    - CVE-2026-43284
    - CVE-2026-43500
mitre_attack_id:
    - T1068
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: endpoint
security_domain: endpoint
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1068/linux_dirtyfrag/kern.log
          source: /var/log/kern
          sourcetype: linux_messages_syslog
      test_type: unit