How do I check whether I am affected by CVE-2026-91487?

- Run `java -version` and compare against the affected releases: 8u503-perf, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27, GraalVM for JDK 17.0.20.1 and 21.0.12.1, GraalVM Enterprise 21.3.19.1.1. - Check which Java runtime your services and build images actually use, including bundled JDKs inside containers.

What is the fix for CVE-2026-91487?

- Upgrade Oracle Java SE to the patched release for your line from the Oracle Critical Patch Update advisory (version numbers not listed in the sources beyond the affected ones; exact fixed builds unknown). - Upgrade Oracle GraalVM for JDK or GraalVM Enterprise Edition to a release newer than the affected builds listed above.

Who is not affected by CVE-2026-91487?

Not affected if: internal-only, no-untrusted-input.

Live › vulnerability › CVE-2026-91487

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medium4.8Runtime

Oracle Java SE Compiler flaw lets unauthenticated network attackers change some data

A flaw in the Compiler component of Oracle Java SE can be triggered over the network by supplying crafted data to its APIs, such as through a web service. A successful attack lets an unauthenticated attacker read and modify a subset of data the Java SE installation can access.

Summary written from the sources below. Check the originals before acting.

CVSS 3.x

4.8

medium

scored by [email protected]

known so far3 of 6

missing: versions, primary source, exploitation

First public: Oct 20, 2026 UTC
Last modified: Oct 21, 2026
Status: open
Known exploitation: None reported
Public exploit: None on GitHub
EPSS: not scored

First seen by InfraStack 2026-10-23 21:57 UTC. All times on this page are UTC.

Why it is medium, and not just CVSS

Likelihood → · Impact ↓

critical

high

medium

high

medium

low

medium

low

Exploited: No reports yet.
Needs login: No.
Needs a special setup: Not known from the sources.
Reachable from: internet.
Worst case: Attacker reads and modifies some data the Java SE runtime can access.
CVSS said: 4.8. The facts above say high; we keep the sources' medium until an analyst looks.

Who is affected

Systems running an affected Oracle Java SE or GraalVM release that expose Java code paths which pass untrusted data into the affected Compiler APIs, such as web services that accept input the server processes through the compiler component. Installations that only run trusted code, or that do not take data from outside the machine, have a much smaller exposure.

Know the next one before it finds you.

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Live › vulnerability › CVE-2026-91487

Go to dashboard

medium4.8Runtime

Oracle Java SE Compiler flaw lets unauthenticated network attackers change some data

Summary written from the sources below. Check the originals before acting.

CVSS 3.x

4.8

medium

scored by [email protected]

known so far3 of 6

missing: versions, primary source, exploitation

First public: Oct 20, 2026 UTC
Last modified: Oct 21, 2026
Status: open
Known exploitation: None reported
Public exploit: None on GitHub
EPSS: not scored

First seen by InfraStack 2026-10-23 21:57 UTC. All times on this page are UTC.

Why it is medium, and not just CVSS

Likelihood → · Impact ↓

critical

high

medium

high

medium

low

medium

low

Exploited: No reports yet.
Needs login: No.
Needs a special setup: Not known from the sources.
Reachable from: internet.
Worst case: Attacker reads and modifies some data the Java SE runtime can access.
CVSS said: 4.8. The facts above say high; we keep the sources' medium until an analyst looks.

Who is affected

Know the next one before it finds you.

Add to Slack

Oracle Java SE Compiler flaw lets unauthenticated network attackers change some data

Why it is medium, and not just CVSS

Who is affected

Know the next one before it finds you.

Oracle Java SE Compiler flaw lets unauthenticated network attackers change some data

Why it is medium, and not just CVSS

Who is affected

Know the next one before it finds you.

How to check

The fix

Who had it, and when

What the sources say, verbatim

Sources