CVE-2026-13759
HIGH 7.5IBM 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
Severe if exploited (CVSS 7.5), but no known exploitation and low modeled probability. Patch on a normal cadence.
Exploitation likelihood
0.3%chance of exploitation in 30 days · 21st percentile
Impact if exploited
7.5CVSS 3.1 · HIGH
- ConfidentialityHigh
- IntegrityHigh
- AvailabilityHigh
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ⚠Privileges: Requires a low-privilege account
- ✓User interaction: No user interaction needed
- ⚠Complexity: Needs a race window or specific setup
✓ lowers the bar for an attacker · ⚠ raises it
Weakness (CWE)
- CWE-502: Deserialization of untrusted data
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H