# CVE-2026-33439: Pre-Authentication Remote Code Execution via `jato.clientSession` Deserialization in OpenAM

- Exploited (CISA KEV): no
- Published: 2026-04-07
- CVSS: 9.3 CRITICAL (v4.0)
- EPSS: 9.3% (95th percentile)
- CWE: CWE-502

Open Access Management (OpenAM) is an access management solution. Prior to 16.0.6, OpenIdentityPlatform OpenAM is vulnerable to pre-authentication Remote Code Execution (RCE) via unsafe Java deserialization of the jato.clientSession HTTP parameter. This bypasses the WhitelistObjectInputStream mitigation that was applied to the jato.pageSession parameter after CVE-2021-35464. An unauthenticated attacker can achieve arbitrary command execution on the server by sending a crafted serialized Java object as the jato.clientSession GET/POST parameter to any JATO ViewBean endpoint whose JSP contains <jato:form> tags (e.g., the Password Reset pages). This vulnerability is fixed in 16.0.6.

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | No public claim | — | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | No public claim | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2026-09-16 | 162 |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### F5

- 2026-09-16 · new · rule 200204093
  > Added: signature 200204093 "OpenAM Unauthenticated Remote Code Execution" (Server Side Code Injection, risk High), systems: Other Web Server. References: CVE-2026-33439.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: passed (0 of 1 requests blocked), template CVE-2026-33439, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: passed (0 of 1 requests blocked), template CVE-2026-33439, 2026-11-02

## Social

1 posts seen since 2026-11-02.

- Exploit repository (unvetted): https://github.com/stapat1245/CVE-2026-33439_poc

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2026-33439 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2026-33439