# 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.

- **Severity:** Critical 9.9 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 16 Sep 2026
- **Updated:** 17 Sep 2026
- **Also known as:** GHSA-phj9-35hx-q9cr

## 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 (Deserialization of Untrusted Data)

## 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.

## Is CVE-2026-20307 being exploited?

There is no known exploitation of CVE-2026-20307 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20307 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-20307 in the wild and no public exploit code.

Affected product: Cisco Identity Services Engine Software. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-20307/ (Markdown: https://insights.sbomify.com/CVE-2026-20307/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20307
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20307
- OSV: https://osv.dev/vulnerability/CVE-2026-20307

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-20307/
Summaries are generated and may contain mistakes; the official description above is the record.