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CVE-2026-13759: IBM WebSphere Extreme Scale 8.6.1.0 through 8.6.1.6 ships three ObjectInputStream subclasses (WsObjectInputStr

38
Routine
HIGH 7.5UPGRADE

CVE-2026-13759 is a high-severity flaw (CVSS 7.5) affecting websphere extreme scale. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

  • High severity

A fixed release or distro patch exists.

Risk facts

CVSS score7.5 (High)
Attack vectorNetwork (remote)
Attack complexityHigh
Privileges neededLow
User interactionNone
EPSS exploit chance0.5% (top 54%)
CISA exploited listNo
WeaknessCWE-502
Published2026-06-30
Last modified2026-10-25
Publisher (CNA): IBM Corporation · Vendor: ibm

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Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

ibm websphere extreme scale UPGRADE
Affected: >= 8.6.1.0 and <= 8.6.1.6
Fixed in: newer than 8.6.1.6
Safe to downgrade to: a release before 8.6.1.0
1. Check installed version
apt-cache policy websphere-extreme-scale || rpm -q websphere-extreme-scale || websphere-extreme-scale --version
2. UPGRADE to newer than 8.6.1.6 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade websphere-extreme-scale
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade websphere-extreme-scale
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 8.6.1.0 (Debian / Ubuntu)
apt-cache madison websphere-extreme-scale sudo apt install websphere-extreme-scale=<VERSION_BEFORE_8.6.1.0> sudo apt-mark hold websphere-extreme-scale
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list websphere-extreme-scale sudo dnf downgrade websphere-extreme-scale-<VERSION_BEFORE_8.6.1.0> sudo dnf versionlock add websphere-extreme-scale
Downgrade risk
Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.
After downgrade
Restart the service, and keep the package held until a fixed release ships.
Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-13759?

websphere extreme scale: upgrade to newer than 8.6.1.6. Exact commands for each OS are on this page.

Is CVE-2026-13759 being exploited?

CVE-2026-13759 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-13759 affect?

CVE-2026-13759 affects websphere extreme scale. Severity is high (CVSS 7.5). 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 t

How urgent is CVE-2026-13759?

Priority 38/100. High severity

Software pages

IBM WebSphere vulnerabilities

Related CVEs

References

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