# CVE-2026-33439: OpenIdentityPlatform OpenAM Java deserialization RCE in jato.clientSession

Source: https://junglewise.ai/threats/cve-2026-33439-openidentityplatform-openam-java-deserialization-rce-in-jato  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-07. Updated: 2026-07-25  
License: CC BY 4.0 with a link back

CVE-2026-33439 · Severity: critical · CVSS 9.8 · Published 2026-04-07

OpenAM is an identity and access management solution used to secure web applications and manage user sessions. A critical security flaw allows an unauthenticated attacker to remotely execute commands on the server by sending a specially crafted web request. This could lead to a total system takeover, theft of sensitive user credentials, and unauthorized access to protected corporate resources.

Technologies: [Open Identity Platform OpenAM](https://junglewise.ai/threats/technologies/openam). Vendors: [Maven](https://junglewise.ai/threats/vendors/maven), [Open Identity Platform](https://junglewise.ai/threats/vendors/open-identity-platform).

## Quick answers

**Is CVE-2026-33439 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-33439 being exploited in the wild.

**How severe is CVE-2026-33439?** Critical severity, with a CVSS score of 9.8, published 7 April 2026.

**Which products and versions are affected?** org.openidentityplatform.openam:openam (Maven) ECOSYSTEM:introduced=0,fixed=16.0.6; Open Identity Platform OpenAM < 16.0.6.

**Is there a fix for CVE-2026-33439?** Yes. org.openidentityplatform.openam:openam (Maven): upgrade to 16.0.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-33439 attacked?** It is attacked over the network, in a hosted service.

**Am I affected by CVE-2026-33439?** Check whether you run org.openidentityplatform.openam:openam (Maven) or Open Identity Platform OpenAM at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.openidentityplatform.openam:openam (Maven): upgrade to 16.0.6 or later

  ```sh
  # set org.openidentityplatform.openam:openam to 16.0.6 in your pom.xml or build.gradle
  ```


## Technical details

OpenIdentityPlatform OpenAM prior to version 16.0.6 is vulnerable to pre-authentication Remote Code Execution (RCE) due to unsafe Java deserialization (CWE-502). The vulnerability exists in the ClientSession.deserializeAttributes() method, which processes the 'jato.clientSession' HTTP parameter using ApplicationObjectInputStream without a class whitelist. This bypasses previous mitigations (CVE-2021-35464) that only addressed the 'jato.pageSession' parameter. An unauthenticated attacker can trigger the exploit by sending a crafted serialized Java object via GET or POST to any JATO ViewBean endpoint containing <jato:form> tags. Successful exploitation allows arbitrary OS command execution under the context of the application server user. The issue is resolved in version 16.0.6 by implementing WhitelistObjectInputStream filtering.

## Affected products

- OpenIdentityPlatform OpenAM < 16.0.6

## Identifiers

- CVE-2026-33439
- GHSA-2cqq-rpvq-g5qj

## Timeline

- 2026-04-07: advisory: GitHub Security Advisory GHSA-2cqq-rpvq-g5qj published
- 2026-04-07: disclosed
- 2026-04-07: patched: Fixed in version 16.0.6

## References

- [https://github.com/OpenIdentityPlatform/OpenAM/security/advisories/GHSA-2cqq-rpvq-g5qj](https://github.com/OpenIdentityPlatform/OpenAM/security/advisories/GHSA-2cqq-rpvq-g5qj)

## Related threats

- [OpenAM default credentials authentication bypass in built-in identities](https://junglewise.ai/threats/cve-2026-123553-openam-before-16-1-4-ships-built-in-identities-in-the-top-level)
- [OpenAM unauthenticated session token disclosure via WebSocket](https://junglewise.ai/threats/cve-2026-123551-openam-from-14-0-0-before-16-1-4-contains-an-information)
- [OpenAM SAML v2.0 service provider authentication bypass](https://junglewise.ai/threats/cve-2026-123550-openam-before-16-1-4-contains-an-authentication-bypass)
- [OpenAM self-registration attribute list enforcement bypass](https://junglewise.ai/threats/cve-2026-123549-openam-before-16-1-4-fails-to-enforce-the-valid-creation)
- [OpenAM open redirect via SAML RelayState](https://junglewise.ai/threats/cve-2026-123547-openam-before-16-1-4-contains-an-open-redirect-vulnerability)