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From Java Byte Stream to Root: Cisco ISE Remote Code Execution Flaws

#cybersecurity #infosec #java #security

From Java Byte Stream to Root: Cisco ISE Remote Code Execution Flaws

Three remote code execution vulnerabilities in Cisco Identity Services Engine (ISE) turn a single crafted request into code execution on the appliance. CERT-In documented them, together with the rest of the ISE flaw set, in advisory CIVN-2026-0462 dated September 17, 2026 with a CRITICAL rating.

The Mechanism

CVE-2026-76176, CVE-2026-20211 and CVE-2026-20307 stem from insecure deserialization of a user-supplied Java byte stream or insufficient validation of user-supplied input. An attacker sends a crafted serialized Java object to the web-based management interface, or an HTTP request to the affected device. Exploitation ends in arbitrary code execution on the device, system-level or user-level access to the underlying operating system, and privilege elevation to root.
Deserialization flaws of this shape are attractive because the payload travels inside data the application is designed to accept. Defense has to happen at the validation layer, not the network perimeter.

The Rest of the Flaw Set

The RCE group is part of a larger disclosure covering ISE and ISE Passive Identity Connector (ISE-PIC):

  • Authentication bypass on an API endpoint: CVE-2026-76460, CVE-2026-20130, CVE-2026-20192, CVE-2026-20194, CVE-2026-20234, CVE-2026-20237, CVE-2026-20287.
  • Command injection via the web management interface: CVE-2026-20305, CVE-2026-20306.
  • SQL injection in REST API calls: CVE-2026-20284.
  • Command injection in the IPsec Open API: CVE-2026-20283.
  • Authenticated write access to the operating system: CVE-2026-20282. The authentication bypass shortens the path to the RCE flaws: an attacker who bypasses management authentication reaches the deserialization endpoints without valid credentials.

Exposure Picture

A ZoomEye query for app="Cisco Identity Services Engine" returns 884047 instances. The fingerprint measures deployed product assets worldwide; it is not a list of compromised hosts. The installed base is large enough that unpatched systems remain a reasonable assumption after disclosure.

Affected Products

  • Cisco Identity Services Engine (ISE)
  • Cisco ISE Passive Identity Connector (ISE-PIC)

Fix and Mitigation

Cisco published fixed releases through five advisories listed under Sources. Patch every ISE and ISE-PIC deployment, and restrict management interface reachability to administration networks while the update rolls out.

Sources

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