MediumCVE-2026-20321

    Cisco Application Policy Infrastructure Controller (APIC): Missing Standardized Error Handling Mechanism (CVE-2026-20321)

    Published Last modified Sources: BSI

    What is affected, what to do

    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.

    Update Application Policy Infrastructure Controller to version 6.0(9h).

    Affected
    • Cisco Application Policy Infrastructure Controller (APIC) eq 5.3(1d)..5.3(1d)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 5.3(2a)..5.3(2a)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 5.3(2b)..5.3(2b)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 5.3(2c)..5.3(2c)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 5.3(2d)..5.3(2d)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 5.3(2e)..5.3(2e)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 5.3(2f)..5.3(2f)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 6.1(5e)..6.1(5e)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 6.2(1f)..6.2(1f)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 6.2(1g)..6.2(1g)
    • Cisco Application Policy Infrastructure Controller (APIC) eq 6.2(2e)..6.2(2e)

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    Metrics

    6.5

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    6.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: BSI

    0.4 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 37.7

    Show all metrics
    Severity
    Medium
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    83.41 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    6.5 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    6.5
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.4 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    37.7
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 8 October 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-544

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    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.

    Source: BSI WID Portal

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    CiscoCisco Application Policy Infrastructure Controller (APIC)
    • 5.2(1g)
    • 5.2(2e)
    • 5.2(2f)
    • 5.2(2g)
    • 5.2(2h)
    • 5.2(3e)
    • 5.2(3f)
    • 5.2(3g)
    • 5.2(4d)
    • 5.2(4e)
    • 5.2(4f)
    • 5.2(4h)
    • 5.2(5c)
    • 5.2(5d)
    • 5.2(5e)
    • 5.2(6e)
    • 5.2(6g)
    • 5.2(6h)
    • 5.2(7f)
    • 5.2(7g)
    • 5.2(8d)
    • 5.2(8e)
    • 5.2(8f)
    • 5.2(8g)
    • 5.2(8h)
    • 5.2(8i)
    • 5.3(1d)
    • 5.3(2a)
    • 5.3(2b)
    • 5.3(2c)
    • 5.3(2d)
    • 5.3(2e)
    • 5.3(2f)
    • 6.0(1g)
    • 6.0(1j)
    • 6.0(2h)
    • 6.0(2j)
    • 6.0(3d)
    • 6.0(3e)
    • 6.0(3g)
    • 6.0(4c)
    • 6.0(5h)
    • 6.0(5j)
    • 6.0(6c)
    • 6.0(6g)
    • 6.0(6h)
    • 6.0(7e)
    • 6.0(8d)
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    Vendors and products

    Weakness classes (CWE)

    • CWE-544Missing Standardized Error Handling Mechanism

      Base

      The product does not use a standardized method for handling errors throughout the code, which might introduce inconsistent error handling and resultant weaknesses.

      Entry at MITRE CWE-544

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-20321","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-10-08T15:33:24.102382Z"}

      Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

    2. ReceivedCisco

      CVSS V3.1: AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N

      Weakness type: CWE-544

      Description added or changed

      Show 5 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      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.
      CVSSadded
      —
      AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N
      Weakness type (CWE)added
      —
      CWE-544
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/20xxx/CVE-2026-20321.json">CVE-2026-20321</a>
      Referenceadded
      —
      https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apic-cmdinj-L6VR4E7

      Source identifier: psirt@cisco.com

    Linked CVEs

    Linked CVEs
    CriticalCVE-2026-76500Cisco Application Policy Infrastructure Controller (APIC): Improper Control of a Resource Through its Lifetime9.8—
    CriticalCVE-2026-76499Cisco Application Policy Infrastructure Controller (APIC): Improper Neutralization9.8—
    CriticalCVE-2026-76498Cisco Application Policy Infrastructure Controller (APIC): Improper Access Control9.8—
    MediumCVE-2026-76488Cisco Application Policy Infrastructure Controller (APIC): Permissions, Privileges, and Access Controls6.5—
    MediumCVE-2026-20321Cisco Application Policy Infrastructure Controller API Command Injection Vulnerability6.5—

    Linked advisories

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    <a href="https://intel.neosec.eu/en/cve/CVE-2026-20321"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-20321.svg?lang=en" alt="CVE-2026-20321 – NEOSEC Intel" height="20"></a>