AL26-021 - Vulnerabilities Impacting Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC) - CVE-2026-20192, CVE-2026-76423 and CVE-2026-76460

CVE-2026-20192 tracks a set of improper access control vulnerabilities (CWE-284) in Cisco Identity Services Engine (ISE) and Cisco ISE Passive Identity Connector (ISE-PIC), discovered by Cisco's own engineering teams during a comprehensive internal security review. The flaws are addressed through a software hardening release rather than an externally reported incident, and Cisco has not disclosed granular per-flaw mechanics in the available data. The CVSS 3.1 score of 10.0 (critical) indicates the issues are remotely exploitable over a network without privileges or user interaction, with high impact to confidentiality, integrity, and availability across security scopes, meaning an attacker could gain broad access or control within affected deployments. All organizations running Cisco ISE or ISE-PIC are potentially affected. There is currently no known exploitation, no public proof-of-concept, and the vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog.

Do: Review Cisco's security advisory (from Cisco PSIRT) to identify which ISE and ISE-PIC releases are affected, and apply the software hardening release as soon as practical. Until patched, restrict access to ISE administration, pxGrid, and passive-identity interfaces to trusted management networks, and monitor Cisco's advisory for updates on exploitation status.

Cisco ISE and Cisco ISE-PIC contain an authentication bypass (CWE-290) in their REST API web service, which is exposed with insufficient authorization checks. An unauthenticated, remote attacker can exploit it by sending a crafted HTTP request to the exposed REST API port, requiring no credentials or user interaction. A successful exploit grants administrative privileges over the device, letting the attacker read and modify ISE configuration and identity data. Any organization running an affected Cisco ISE or ISE-PIC deployment is affected, with risk highest where the REST API port is reachable from untrusted networks. No public proof-of-concept or in-the-wild exploitation is currently known, and the flaw is not yet listed in CISA's KEV catalog.

Do: Upgrade ISE and ISE-PIC to the fixed releases identified in the Cisco PSIRT advisory for CVE-2026-76423. As an interim mitigation, restrict network access to the ISE REST API port to trusted management networks and disable the REST API service where it is not required. Review ISE logs for unauthenticated or anomalous administrative API requests, and treat configuration and identity data on exposed deployments as potentially compromised.

Cisco Identity Services Engine (ISE) and the Cisco ISE Passive Identity Connector (ISE-PIC) contain an incorrect use of privileged APIs flaw (CWE-648) affecting the web-based management interface. An unauthenticated, remote attacker with network access to that interface can send requests that invoke privileged APIs without authenticating, bypassing the interface's access controls. Successful exploitation grants the attacker unauthorized access to the affected device, presumably with the administrative capabilities available through the management interface, such as control over network access policy and visibility into identity data. Any organization running an affected Cisco ISE or ISE-PIC release is potentially affected, with risk highest where the management interface is reachable from untrusted networks. The flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2026-09-16, indicating exploitation in the wild, though no public proof-of-concept is known and CVSS scoring is pending.

Do: Upgrade ISE and ISE-PIC to the fixed releases specified in Cisco's security advisory (fixed versions are not provided in the available data); because the flaw is on CISA's KEV list, federal agencies must patch or apply mitigations per BOD 26-04 timelines. Until patched, restrict access to the web-based management interface to trusted administrative networks only, verify no unintended exposure via firewalls/ACLs, and monitor for unauthenticated access attempts against the interface.