ZeroHour

CVE-2026-20176

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Authenticated Command Injection in Cisco Identity Services Engine (ISE)

CVSS 3.1
9.1 critical
EPSS
Published
()
Modified
AI analysis

Cisco ISE contains a command injection flaw (CWE-77) caused by insufficient validation of user-supplied input. An authenticated, remote attacker who already holds valid high-privileged administrative credentials can send a crafted HTTP request to an affected device to run arbitrary commands on the underlying operating system, gaining system-level access and then elevating to root. In single-node deployments, successful exploitation can render the ISE node unavailable, causing a denial of service in which endpoints that have not yet authenticated cannot access the network until the node is restored. All Cisco ISE deployments are potentially affected, though exploitation requires stolen or compromised administrator credentials rather than anonymous access. No public proof-of-concept is known and the flaw is not listed in CISA's KEV, so exploitation has not been confirmed.

What to do: Upgrade to the fixed release specified in Cisco's PSIRT advisory for CVE-2026-20176 (not listed in this data). Until patched, restrict access to the ISE administration interface to trusted management networks, audit high-privileged admin accounts for compromise (since valid admin credentials are required), and monitor for unexpected root-level or shell activity on ISE appliances. Operators of single-node deployments should prepare failover/restore plans, as exploitation would block new endpoint network authentication until the node is recovered.

Affected
Cisco Identity Services Engine (ISE)
Estimated exposure
largelikely tens of thousands of enterprise ISE deployments/nodes worldwide (estimated) — Cisco ISE is the dominant enterprise network access control (NAC) platform widely deployed in large enterprise and campus networks, but Cisco does not publish install counts, so this order of magnitude is inferred from its market position;…

Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.

Description

A vulnerability in Cisco ISE could allow an authenticated, remote attacker to execute arbitrary commands on the underlying operating system of an affected device. To exploit this vulnerability, the attacker must have valid high-privileged administrative credentials. This vulnerability is due to insufficient validation of user-supplied input. An attacker could exploit this vulnerability by sending a crafted HTTP request to an affected device. A successful exploit could allow the attacker to obtain system-level access to the underlying operating system and then elevate privileges to root. In single-node deployments, successful exploitation of this vulnerability could cause the affected ISE node to become unavailable, resulting in a DoS condition. In that condition, endpoints that have not already authenticated would be unable to access the network until the node is restored.

Weakness
CWE-77
Vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

In the news

Cisco Warns of New Zero-Day ISE Auth Bypass (CVSS 10.0) Exploited in Active Attacks

Cisco warns CVE-2026-76460 (CVSS 10.0), an unauthenticated ISE auth bypass leading to root command execution, is under active exploitation and was added to CISA's KEV.

Cisco warned that CVE-2026-76460 (CVSS 10.0), an insufficient-authentication flaw in an Identity Services Engine (ISE) API endpoint, is being actively exploited by unauthenticated remote attackers and can yield root-privilege command execution on ISE and ISE-PIC regardless of configuration. Fixes shipped across ISE 3.1 through 3.5 patch branches; Cisco advised reviewing access.log for unexpected usernames (e.g., "dummyuser"), re-imaging affected nodes, and using iACLs, since no workarounds exist. CISA added the flaw to its KEV catalog on September 16, 2026, requiring FCEB agencies to patch by September 19. Cisco simultaneously issued 77 new CVEs, 41 affecting ISE and 28 affecting Secure Firewall products, days after confirming active exploitation of CVE-2026-76461 in Secure Email Gateway.

Cisco warns of max severity ISE zero-day exploited in attacks

Cisco patched CVE-2026-76460, a maximum-severity authentication bypass in Identity Services Engine actively exploited in attacks; CISA added it to KEV with a three-day federal deadline.

CVE-2026-76460 is a maximum-severity authentication bypass in an API endpoint of Cisco Identity Services Engine (ISE) and ISE-PIC, exploitable regardless of configuration, allowing attackers to access the web-based management interface. Cisco PSIRT confirmed active exploitation; no workarounds exist, and fixed releases are available for ISE 3.1 through 3.5, with re-imaging of suspect nodes recommended. CISA added the flaw to its Known Exploited Vulnerabilities Catalog and ordered federal agencies to patch within three days. Cisco also patched CVE-2026-76423 and five other critical ISE flaws (CVE-2026-20176, CVE-2026-20211, CVE-2026-20307, CVE-2026-20284) that are not yet flagged as exploited.

BleepingComputer · 7h agoExploit / PoC in the wildCVE-2026-76460CVE-2026-76423CVE-2026-20176+4 CVEs1· 1 read