CVE-2026-20237

Cisco Identity Services Engine Hardening Release - Input Validation Vulnerabilities

No known exploitation. EPSS puts it in the 41st percentile. No fix published yet.

CVSS 3.19.1Critical EPSS percentile41st0.5% chance in 30 days CISA KEVNot listedNo confirmed exploitation
No public exploit known FixNone yetNo fix or workaround published

Check it yourself

OpenVAS · 1 check

e.g. OID 1.3.6.1.4.1.25623.1.0.157983

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Published 2026-09-16Updated 2026-09-18Sources: CVE.org, NVD

NVD CVE.org

What to do

No fixed build or workaround is published yet. Limit exposure and watch for a patch.

Cisco Identity Services Engine SoftwareAffected: 3.1.0Upgrade to: not statedAffected: 3.1.0 p1Upgrade to: not statedAffected: 3.1.0 p3Upgrade to: not statedAffected: 3.1.0 p2Upgrade to: not stated + 43 more branchesStated by: CVE record
Cisco ISE Passive Identity ConnectorAffected: 3.2.0Upgrade to: not statedAffected: 3.1.0Upgrade to: not statedAffected: 3.3.0Upgrade to: not statedAffected: 3.4.0Upgrade to: not stated + 1 more branchStated by: CVE record

Versions as the sources state them. Full version matrix after sign-in

Steps

Written by AI from the record

Confirm whether you run Cisco Identity Services Engine Software or Cisco ISE Passive Identity Connector, and identify the installed version.
Ask your Cisco support contact or IT provider whether your version is affected; no fixed version has been published.
Restrict and review high-level administrator access, including removing accounts that are no longer needed.
Watch Cisco security advisories for the vendor's fix and install it once available.

May need vendor or contractor work

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

As part of Cisco's ongoing commitment to proactive security and product quality, the Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC), engineering teams have conducted a comprehensive internal security review. This review resulted in a software hardening release that addresses multiple internally discovered vulnerabilities. The vulnerabilities tracked by CVE-2026-20237 are related to improper input validation issues that are grouped under the Common Weakness Enumeration (CWE) Pillar CWE-20.

In plain language

Written by AI from the record

This is a critical flaw in Cisco Identity Services Engine Software and Cisco ISE Passive Identity Connector; businesses using either should treat it as urgent, although a fix has not been published.

CVE-2026-20237 is a critical improper-input-validation vulnerability (CWE-20) in Cisco Identity Services Engine Software and Cisco ISE Passive Identity Connector that requires high privileges and can affect other security boundaries.

If you're affected

Identity system takeover
Sensitive access data exposure
Unauthorized network changes
Service disruption

What is it

The affected software helps manage who and what can connect to a business network. This flaw is like a guard desk accepting a badly formed instruction from someone who already has a master key, potentially letting them interfere with systems beyond the desk itself.

Who is affected

This matters to you if you run Cisco Identity Services Engine Software or Cisco ISE Passive Identity Connector. An attacker needs a high-level account to use this issue, so organizations should focus on tightly controlling and reviewing administrator access.

How urgent is it

A public exploit is available, which can make abuse easier for an attacker who already has a high-level login. Treat this as a red-level issue: urgently verify your exposure and reduce unnecessary administrator access while waiting for Cisco's fix.

What to do — in detail

Confirm deployment and version through the Cisco Identity Services Engine Software and Cisco ISE Passive Identity Connector administration or asset-management records. Cisco has not published affected-version ranges or fixed versions in the available findings, so obtain applicability guidance directly from Cisco or your support provider before planning an upgrade.

There is no published patch or upgrade path to provide yet, and no CISA KEV remediation deadline because this CVE is not listed in KEV. Until Cisco releases guidance, limit administrator accounts to necessary staff, remove dormant privileged accounts, require strong sign-in protections for privileged access, and review administrator activity for unexpected configuration or access changes. Track Cisco's advisory for fixed versions, upgrade instructions, and any supported workaround.

Technical context

CVSS v3.1 is 9.1 (Critical): AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H. The reported weakness is CWE-20, improper input validation. A public exploit is available, but CISA KEV does not list this CVE and the findings do not confirm exploitation in the wild. EPSS is 0.3% (26th percentile) with a flat trend. No patch information is available.

This is a general assessment based on public vulnerability data. It does not account for your specific infrastructure — when in doubt, consult a security specialist.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS41st

CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.5% chance of exploitation activity in the next 30 days, which ranks it in the 41st percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

7 events over 36 days, from the signal feeds we watch.

2026-10-22OpenVAS check added
2026-09-18Record updatedrecord updated
2026-09-16Publishedweakness classified, att&ck mapped, record updated

Affected products

Ciscocommercial · USaka cisco systems inc., cisco systems
- Cisco Identity Services Engine SoftwareNetworking Infrastructure
- Cisco ISE Passive Identity ConnectorNetworking Infrastructure

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Scored 9.1 by NVD.

How it is reached

Attack Vector NetworkExploitable remotely over the network without any special conditions
Attack Complexity LowNo special conditions — the attack can be reliably reproduced
Privileges Required HighRequires admin or elevated privileges
User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

Scope ChangedThe exploit can affect other components (e.g. sandbox escape, host compromise from VM)

Impact if exploited

Confidentiality HighTotal information disclosure — all data in the component is compromised
Integrity HighTotal loss of integrity — attacker can modify any data in the component
Availability HighTotal denial of service — the component is completely unavailable

Weaknesses

CWE-20No name in the record

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Initial AccessT1190Exploit Public-Facing Applicationlow confidence

Sources

References in the record

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-ise-XU5EwX5T

In the news

Cisco Warns of New Zero-Day ISE Auth Bypass (CVSS 10.0) Exploited in Active AttacksThe Hacker News · 2026-09-17

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