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Websphere Extreme ScaleApplication · Ibm

CVE-2026-13759

HIGH · 8.8 CVSS v3.1 Published 2026-06-30
Fix available
A fix is available. Upgrade to after 8.6.1.6 or later.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable Zero-click 8 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

IBM WebSphere Extreme Scale 8.6.1.0-8.6.1.6 ships three ObjectInputStream subclasses (WsObjectInputStream, ObjectStreamPool$ReusableInputStream, ObjectInputStreamResolver) lacking JEP-290 deserialization filters; when Oracle Coherence is on the classpath, this enables exploitation of RemoteConstructor.readResolve and PriorityQueue/ExtractorComparator gadget chains, allowing authenticated users with session attribute write access or LAN-adjacent grid replication attackers to execute arbitrary code on peer WAS JVMs.

MitigationApply JEP-290 deserialization filters to the three vulnerable ObjectInputStream subclasses, or upgrade to a patched release, or remove Coherence from the classpath if not required.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Websphere Extreme ScaleApplication
Affected:>= 8.6.1.0, <= 8.6.1.6

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify IBM WebSphere Extreme Scale version
    Run 'java -jar <install_dir>/bin/wxsVersion.jar' or check the product JAR manifest in the installation directory for version 8.6.1.x
    Affected if Version is 8.6.1.0 through 8.6.1.6 inclusive
  2. Check for Oracle Coherence on classpath
    Search for coherence*.jar files in the application lib directory, classpath configuration, or runtime classloader dump; grep for 'coherence' in manifest files or startup scripts
    Affected if Coherence JARs are present on the classpath alongside WebSphere Extreme Scale
  3. Locate vulnerable ObjectInputStream subclasses
    Inspect compiled classes or JARs in the WebSphere Extreme Scale installation for WsObjectInputStream, ObjectStreamPool$ReusableInputStream, and ObjectInputStreamResolver classes; decompile or examine bytecode for presence of custom readObject methods without JEP-290 filter validation
    Affected if These three classes exist without JEP-290 deserialization filter implementation
  4. Verify grid replication listeners are exposed
    Check XML configuration files (e.g., objectgrid.xml, grid topology configs) for replication listener ports and addresses; examine network bindings for replication transport
    Affected if Grid replication endpoints are bound to accessible network interfaces, especially untrusted LAN segments
  5. Check session attribute write access
    Review session management configuration for whether authenticated users can write to session attributes; examine session listener and servlet configurations for attribute set operations
    Affected if Authenticated users have write access to session attributes without additional authorization controls

Environment is affected if IBM WebSphere Extreme Scale version 8.6.1.0-8.6.1.6 is installed, Oracle Coherence is on the classpath, the three vulnerable ObjectInputStream subclasses lack JEP-290 filters, and the grid replication or session management is network-accessible to attackers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to a release after 8.6.1.6
Interim mitigation

Apply JEP-290 deserialization filters to the three vulnerable ObjectInputStream subclasses, or upgrade to a patched release, or remove Coherence from the classpath if not required.

Fix this in Websphere Extreme Scale Scoped from the published advisory
  • Consultation2.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
23.0 hours of engineering $4,000
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-13759 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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