CVE-2026-20307 Cisco Identity Services Engine Remote Code Execution Vulnerability
Authenticated attackers can execute arbitrary code and gain root privileges via insecure Java deserialization in Cisco ISE.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-20307?
CVE-2026-20307 is a critical unsafe deserialization vulnerability in Cisco Identity Services Engine Software, published on 16 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
A vulnerability in the web-based management interface of 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 at least low-privileged administrative credentials. This vulnerability is due to insecure deserialization of a user-supplied Java byte stream. An attacker could exploit this vulnerability by sending a crafted serialized Java object to the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary code on the device and 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 denial of service (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-502
Which versions are affected by CVE-2026-20307?
How do I fix CVE-2026-20307?
No fix has been published for CVE-2026-20307 yet. Limit exposure of the affected software until one is available.
Upgrade, and only deserialise data from trusted sources or with an allow-list of types. More about Unsafe deserialization.
Is CVE-2026-20307 being exploited?
There is no known exploitation of CVE-2026-20307 in the wild and no public exploit code.
Sources
Also known as GHSA-phj9-35hx-q9cr.