Cisco IOS XE WebUI Login From IOSd Local Port

Status: production
Severity: medium
Group by: dest, reason, src_ip, user
Author: Nasreddine Bencherchali
Source: github.com/splunk/security_content

This analytic detects Cisco IOS-XE WebUI authentication failure and success logs that include local port 21111. This is a strong an indicator of WebUI exploitation because normal users should not authenticate through the underlying IOS-XE Linux shell path.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1078` Valid Accounts, `T1190` Exploit Public-Facing Application
Persistence	`T1078` Valid Accounts
Privilege Escalation	`T1078` Valid Accounts
Stealth	`T1078` Valid Accounts

Rule body splunk

name: Cisco IOS XE WebUI Login From IOSd Local Port
id: 77a1751f-552f-456c-b9ae-cdb66eec3e42
version: 1
creation_date: '2026-05-19'
modification_date: '2026-05-19'
author: Nasreddine Bencherchali
status: production
type: TTP
description: |
    This analytic detects Cisco IOS-XE WebUI authentication failure and success logs that include local port 21111.
    This is a strong an indicator of WebUI exploitation because normal users should not authenticate through the underlying IOS-XE Linux shell path.
data_source:
    - Cisco IOS Logs
search: |-
    `cisco_ios`
    facility="SEC_LOGIN"
    mnemonic IN ("QUIET_MODE_ON", "LOGIN_SUCCESS", "LOGIN_FAILED")
    message_text="*[localport: 21111]*"
    | rex field=_raw "\[user:\s*(?<user>[^\]]+)\]"
    | rex field=_raw "\[Source:\s*(?<src_ip>[^\]]+)\]"
    | rex field=_raw "\[localport:\s*(?<local_port>[^\]]+)\]"
    | rex field=_raw "\[Reason:\s*(?<reason>[^\]]+)\]"
    | rex field=_raw "\[ACL:\s*(?<acl>[^\]]+)\]"
    | eval dest=coalesce(host, dvc, dest, "unknown")
    | stats count min(_time) as firstTime
                  max(_time) as lastTime
                  values(local_port) as local_port
                  values(acl) as acl
      by dest user src_ip reason
    | `security_content_ctime(firstTime)`
    | `security_content_ctime(lastTime)`
    | `cisco_ios_xe_webui_login_from_iosd_local_port_filter`
how_to_implement: |
    Use the Cisco Catalyst Add-on for Splunk (https://splunkbase.splunk.com/app/7538) to Ingest Cisco IOS-XE syslog with sourcetype "cisco:ios".
    Login failure logging must be enabled with "login on-failure log".
known_false_positives: |
    This local port value should not appear for normal WebUI logins. So false positives should very minimal.
references:
    - https://www.cisa.gov/news-events/cybersecurity-advisories/aa25-239a
    - https://blog.talosintelligence.com/salt-typhoon-analysis/
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: WebUI authentication failure with local port 21111 from $src_ip$.
    entity:
        field: user
        type: user
        score: 50
intermediate_findings:
    entities:
        - field: dest
          type: system
          score: 50
          message: WebUI authentication failure with local port 21111 from $src_ip$ on $dest$.
threat_objects:
    - field: src_ip
      type: ip_address
analytic_story:
    - Salt Typhoon
asset_type: Network
mitre_attack_id:
    - T1190
    - T1078
product:
    - Splunk Enterprise
    - Splunk Enterprise Security
    - Splunk Cloud
category: application
security_domain: network
tests:
    - name: True Positive Test
      attack_data:
        - data: https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/emerging_threats/SaltTyphoon/salttyphoon_cisco.log
          source: ctb:catalyst:syslog
          sourcetype: cisco:ios
      test_type: unit

Stages and Predicates

Stage 1: `search`

`cisco_ios`
facility="SEC_LOGIN"
mnemonic IN ("QUIET_MODE_ON", "LOGIN_SUCCESS", "LOGIN_FAILED")
message_text="*[localport: 21111]*"

Stage 2: `rex`

| rex field=_raw "\[user:\s*(?<user>[^\]]+)\]"

Stage 3: `rex`

| rex field=_raw "\[Source:\s*(?<src_ip>[^\]]+)\]"

Stage 4: `rex`

| rex field=_raw "\[localport:\s*(?<local_port>[^\]]+)\]"

Stage 5: `rex`

| rex field=_raw "\[Reason:\s*(?<reason>[^\]]+)\]"

Stage 6: `rex`

| rex field=_raw "\[ACL:\s*(?<acl>[^\]]+)\]"

Stage 7: `eval`

| eval dest=coalesce(host, dvc, dest, "unknown")

Stage 8: `stats`

| stats count min(_time) as firstTime
              max(_time) as lastTime
              values(local_port) as local_port
              values(acl) as acl
  by dest user src_ip reason

Stage 9: `search`

| `security_content_ctime(firstTime)`

Stage 10: `search`

| `security_content_ctime(lastTime)`

Stage 11: `search`

| `cisco_ios_xe_webui_login_from_iosd_local_port_filter`

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.

Field	Kind	Values
`facility`	eq	`"SEC_LOGIN"`
`message_text`	eq	`"[localport: 21111]"`
`mnemonic`	in	`"LOGIN_FAILED"` `"LOGIN_SUCCESS"` `"QUIET_MODE_ON"`
`sourcetype`	eq	`cisco:ios`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Cisco IOS XE WebUI Login From IOSd Local Port

MITRE ATT&CK coverage

Rule body splunk

Stages and Predicates

Stage 1: `search`

Stage 2: `rex`

Stage 3: `rex`

Stage 4: `rex`

Stage 5: `rex`

Stage 6: `rex`

Stage 7: `eval`

Stage 8: `stats`

Stage 9: `search`

Stage 10: `search`

Stage 11: `search`

Indicators

Keyboard shortcuts

Search operators

Cisco IOS XE WebUI Login From IOSd Local Port

MITRE ATT&CK coverage

Rule body splunk

Stages and Predicates

Stage 1: search

Stage 2: rex

Stage 3: rex

Stage 4: rex

Stage 5: rex

Stage 6: rex

Stage 7: eval

Stage 8: stats

Stage 9: search

Stage 10: search

Stage 11: search

Indicators

Stage 1: `search`

Stage 2: `rex`

Stage 3: `rex`

Stage 4: `rex`

Stage 5: `rex`

Stage 6: `rex`

Stage 7: `eval`

Stage 8: `stats`

Stage 9: `search`

Stage 10: `search`

Stage 11: `search`