# Cisco IOS XE web UI zero-days: implants on tens of thousands of devices · pwn.watch

> Attackers chained two zero-days in the Cisco IOS XE web UI. CVE-2023-20198 let them create a privilege-15 account, and CVE-2023-20273 let them write a root-level implant. Internet scans soon found implants on tens of thousands of switches and routers.

Page: https://pwn.watch/i/cisco-ios-xe-web-ui-implants-cve-2023-20198 · generated 2026-10-22T20:45:43.249Z

## Status
- Severity: critical · status: closed · patch: patched
- Product: Cisco IOS XE Software (web UI)
- Started: 2023-09-18 · closed: 2023-10-23
- CVEs: CVE-2023-20198, CVE-2023-20273
- Affected: IOS XE with the HTTP/HTTPS server (web UI) enabled; see vendor advisory
- Fixed in: 17.9.4a; 17.6.6a; 17.3.8a; 16.12.10a (Catalyst 3650/3850 only)

## Follow this incident
- RSS (one item per update): https://pwn.watch/i/cisco-ios-xe-web-ui-implants-cve-2023-20198/feed.xml
- JSON Feed: https://pwn.watch/i/cisco-ios-xe-web-ui-implants-cve-2023-20198/feed.json
- Full data (timeline, sources, posts, agentBrief): https://pwn.watch/i/cisco-ios-xe-web-ui-implants-cve-2023-20198.json
- This file: https://pwn.watch/i/cisco-ios-xe-web-ui-implants-cve-2023-20198/llms.txt

## Updates (newest first)
- 2023-10-23: CISA adds CVE-2023-20273 to the KEV catalog
- 2023-10-22: First fixed release, 17.9.4a, published (https://www.cisco.com/c/en/us/support/docs/csa/cisco-sa-iosxe-webui-privesc-j22SaA4z.html)
- 2023-10-20: Cisco discloses the second bug (CVE-2023-20273) used to write the implant as root
- 2023-10-16: Cisco advisory and Talos write-up on active exploitation; CISA adds CVE-2023-20198 to KEV (https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-webui-privesc-j22SaA4z)
- 2023-09-18: Earliest malicious activity found by Cisco Talos (https://blog.talosintelligence.com/active-exploitation-of-cisco-ios-xe-software/)

## Fix brief
# Security brief: Cisco IOS XE web UI zero-days: implants on tens of thousands of devices

Source: https://pwn.watch/i/cisco-ios-xe-web-ui-implants-cve-2023-20198 · status: closed (closed Oct 23, 2023) · severity: critical · updated Oct 23, 2023

## Patch status
**PATCHED: fixed releases exist. Upgrade to a fixed version.**

## What it is
Attackers chained two zero-days in the Cisco IOS XE web UI. CVE-2023-20198 let them create a privilege-15 account, and CVE-2023-20273 let them write a root-level implant. Internet scans soon found implants on tens of thousands of switches and routers.

Severity detail: CVSS 10.0 (CVE-2023-20198), zero-day, actively exploited (CISA KEV)

- Product: Cisco IOS XE Software (web UI)
- CVE / advisory ids: CVE-2023-20198, CVE-2023-20273

## Affected versions
- IOS XE with the HTTP/HTTPS server (web UI) enabled; see vendor advisory

## Check whether you're affected
No generic command applies (the product is a hosted service, appliance or desktop app). Check the installed version in its admin UI / About screen and compare with the versions above.

## Fix
Upgrade to one of these fixed versions (or later on the same branch):
- 17.9.4a
- 17.6.6a
- 17.3.8a
- 16.12.10a (Catalyst 3650/3850 only)

After upgrading, re-run the checks above and redeploy/restart the affected services.

## Latest updates
- Oct 23, 2023: CISA adds CVE-2023-20273 to the KEV catalog
- Oct 22, 2023: First fixed release, 17.9.4a, published
- Oct 20, 2023: Cisco discloses the second bug (CVE-2023-20273) used to write the implant as root
- Oct 16, 2023: Cisco advisory and Talos write-up on active exploitation; CISA adds CVE-2023-20198 to KEV
- Sep 18, 2023: Earliest malicious activity found by Cisco Talos

## Advisories
- [Multiple Vulnerabilities in Cisco IOS XE Software Web UI Feature](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-webui-privesc-j22SaA4z) (Cisco)
- [Guidance for Addressing Cisco IOS XE Web UI Vulnerabilities](https://www.cisa.gov/guidance-addressing-cisco-ios-xe-web-ui-vulnerabilities) (CISA)
- [NVD: CVE-2023-20198](https://nvd.nist.gov/vuln/detail/CVE-2023-20198) (NVD)
- [NVD: CVE-2023-20273](https://nvd.nist.gov/vuln/detail/CVE-2023-20273) (NVD)
- [CISA Known Exploited Vulnerabilities Catalog](https://www.cisa.gov/known-exploited-vulnerabilities-catalog) (CISA)

## Write-ups & news
- [Active exploitation of Cisco IOS XE Software Web Management User Interface vulnerability](https://blog.talosintelligence.com/active-exploitation-of-cisco-ios-xe-software/)

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Machine-readable: https://pwn.watch/i/cisco-ios-xe-web-ui-implants-cve-2023-20198.json · all incidents: https://pwn.watch/incidents.json. Verify against the vendor advisory before changing production systems.