CVE-2026-13759 IBM WebSphere eXtreme Scale is affected by Insecure Deserilization

What is CVE-2026-13759?

CVE-2026-13759 is a high-severity unsafe deserialization vulnerability in IBM WebSphere Extreme Scale, published on 30 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.

Official description

IBM WebSphere Extreme Scale 8.6.1.0 through 8.6.1.6 ships three ObjectInputStream subclasses (WsObjectInputStream, ObjectStreamPool$ReusableInputStream, ObjectInputStreamResolver) that install no JEP-290 class filter; when Coherence is on the classpath, multiple RCE gadget chains including RemoteConstructor.readResolve and PriorityQueue/ExtractorComparator are confirmed working, allowing a post-login attacker who can write a session attribute or a LAN-adjacent attacker on the grid replication wire to execute arbitrary code on peer WAS JVMs

Weakness: CWE-502

Which versions are affected by CVE-2026-13759?

It affects 1 product.

Products include Ibm Websphere Extreme Scale.

How do I fix CVE-2026-13759?

No fix has been published for CVE-2026-13759 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-2026-13759 being exploited?

There is no known exploitation of CVE-2026-13759 in the wild and no public exploit code.

Other vulnerabilities in IBM WebSphere Extreme Scale

• CVE-2026-13772 IBM WebSphere eXtreme Scale's OQL is affected by remote code execution High 7.5
• CVE-2013-5393 Auth bypass in n/a High 7.5
• CVE-2026-9002 IBM WebSphere eXtremes Scale is affected by uncontrolled resource consumption when XDF is enabled Medium 6.5
• CVE-2019-4109 Cross-site scripting in WebSphere eXtreme Scale Medium 6.1
• CVE-2016-0400 Other in n/a Medium 6.1

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-xw6m-6cgm-v7qm.