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Critical Oracle Java Vulnerability CVE-2026-91403 Disclosed

Critical Oracle Java Vulnerability CVE-2026-91403 Disclosed

First seen 22 Oct 2026, 07:38 UTC • •
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ThreatCluster AI
ThreatCluster •October 22, 2026 at 09:14 UTC
  • •CVE-2026-91403 has a CVSS score of 9.1, indicating critical severity.
  • •Affected systems include multiple versions of Oracle Java SE and GraalVM.
  • •The vulnerability allows unauthenticated attackers to manipulate critical data.

A critical vulnerability, CVE-2026-91403, has been identified in Oracle Java SE and GraalVM products. Affected versions include Oracle Java SE 8u511, 11.0.33, 17.0.21, and others, as well as GraalVM for JDK 17.0.21 and 21.0.13. The flaw allows unauthenticated attackers with network access to exploit the vulnerability, leading to unauthorized data manipulation and access. The vulnerability can be exploited via APIs, including through web services that supply data to these APIs. The CVSS score for this vulnerability is 9.1, indicating a critical severity level. Users are urged to apply patches as they become available. The vulnerability was published on October 21, 2026.

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Timeline

2026-10-21
CVE-2026-91403 published
Oracle disclosed a critical vulnerability affecting multiple Java SE and GraalVM versions.
Cve

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Common questions

Which versions are affected?
Affected versions include Oracle Java SE 8u511, 11.0.33, 17.0.21, and others, as well as GraalVM for JDK 17.0.21 and 21.0.13.
What is the severity of this vulnerability?
CVE-2026-91403 has a CVSS score of 9.1, indicating it is critical.
What should organizations do?
Organizations should monitor for patches and apply them as soon as they are available to mitigate the risk.