Vulnerability · Published Jun 30, 2026 · Assigned by ibm

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

High 7.5

In plain English

A high-severity unsafe deserialization in WebSphere Extreme Scale from IBM. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 46% of all known vulnerabilities).

Severity (CVSS 3.1)7.5High

Exploit odds (30 days)0.5%top 54.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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

Affected products (as reported)

Vendor	Product	Versions
IBM	WebSphere Extreme Scale	8.6.1.0 – through 8.6.1.6

Weakness: CWE-502 · Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

References

https://www.ibm.com/support/pages/node/7278595 vendor-advisory, patch