CVE-2026-13759
High
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
SeverityHigh
CVSS7.5
Exploit probability—
Product
Ibm Websphere Extreme Scale
PublishedJun 30, 2026
First seenJun 30, 2026
Weakness typeCWE-502Deserialization of untrusted data
How to fix
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| ibm websphere_extreme_scale | 8.6.1.0 ≤ v ≤ 8.6.1.6 | — |
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