What is CVE-2026-13759?

CVE-2026-13759 is a high-severity vulnerability in Ibm Websphere Extreme Scale, classified under Deserialization of Untrusted Data. CVSS score: 7.5/10. Published 2026-06-30.

How severe is CVE-2026-13759?

High severity. CVSS v3 base score is 7.5 out of 10.

Deserialization in Ibm Websphere Extreme Scale

CVE-2026-13759

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

Vulnerability class: Insecure Deserialization

EPSS: 0.003 (22.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H.

Affected products

Ibm Websphere Extreme Scale — versions 8.6.1.0
Ibm Websphere_extreme_scale

Weakness classification (CWE)

CWE-502 — Deserialization of Untrusted Data

References

psirt@us.ibm.com (vendor-advisory, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-13759?: CVE-2026-13759 is a high-severity vulnerability in Ibm Websphere Extreme Scale, classified under Deserialization of Untrusted Data. CVSS score: 7.5/10. Published 2026-06-30.
How severe is CVE-2026-13759?: High severity. CVSS v3 base score is 7.5 out of 10.