# CVE-2026-20321 — Cisco Application Policy Infrastructure Controller (APIC)

> As of 2026-10-08, CVE-2026-20321 is a MEDIUM-severity vulnerability in Cisco Application Policy Infrastructure Controller (APIC), CVSS v3.1 6.5, EPSS 0.4% (35.7th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-20321, most recently “Cisco October 2026 Security Advisories: Critical Flaws in Meraki, License (SSM) On-Prem, NX-OS, APIC and Finesse (CVE-2026-76464, CVE-2026-20328, CVE-2026-76485 and others)”.

**Last updated:** 2026-10-08

## What is CVE-2026-20321?

A vulnerability in the web-based management API for Cisco Application Policy Infrastructure Controller (APIC) could allow an authenticated, remote attacker to execute arbitrary commands as the root user. To exploit this vulnerability, the attacker must have valid administrative credentials. This vulnerability is due to insufficient input validation of user-controlled command arguments. An attacker could exploit this vulnerability by authenticating using the API and sending crafted input. A successful exploit could allow the attacker to execute arbitrary commands on the underlying operating system of an affected device with root-level privileges.

The record classifies CVE-2026-20321 under weakness class [CWE-544](https://cwe.mitre.org/data/definitions/544.html). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs high-privilege credentials, needs no user interaction, and has high impact on confidentiality, integrity. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 3 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 6.5 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N`)
- **EPSS (FIRST):** 0.4% probability of exploitation in the next 30 days, higher than 35.7% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-10-07, last modified 2026-10-08

## Is CVE-2026-20321 being exploited?

It currently carries a trending score of 43 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [Cisco](https://intel.threadlinqs.com/vendors/cisco): Application Policy Infrastructure Controller (APIC)

## How to fix CVE-2026-20321

No vendor patch reference has been recorded for CVE-2026-20321 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-20321

1 tracked threat in the Threadlinqs corpus references CVE-2026-20321, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Cisco October 2026 Security Advisories: Critical Flaws in Meraki, License (SSM) On-Prem, NX-OS, APIC and Finesse (CVE-2026-76464, CVE-2026-20328, CVE-2026-76485 and others)](https://intel.threadlinqs.com/threat/TL-2026-3108) — CRITICAL · 2026-10-09

## Sources

Enriched from CVE.org, FIRST EPSS. Last verified by Threadlinqs on 2026-10-10.

**Other references**

- [sec.cloudapps.cisco.com](https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apic-cmdinj-L6VR4E7)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-20321
Full detection coverage and IOCs for threats exploiting CVE-2026-20321 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp