CVE-2026-83400

MEDIUM CVSS 5.3
Published: 2026-10-20
Modified: 2026-10-21
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AI Threat Summary

CVE-2026-83400 is a moderate vulnerability with a CVSS score of 5.3 affecting the target software. Authentication can be bypassed allowing unauthenticated access. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

Vulnerability in the Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition product of Oracle Java SE (component: JAXP). Supported versions that are affected are Oracle Java SE: 8u503, 8u503-perf, 11.0.32.1, 17.0.20.1, 21.0.12.1, 25.0.4.1, 27; Oracle GraalVM for JDK: 17.0.20.1 and 21.0.12.1; Oracle GraalVM Enterprise Edition: 21.3.19.1.1. Easily exploitable vulnerability allows unauthenticated attacker with network access via multiple protocols to compromise Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition. Successful attacks of this vulnerability can result in unauthorized ability to cause a partial denial of service (partial DOS) of Oracle Java SE, Oracle GraalVM for JDK, Oracle GraalVM Enterprise Edition. Note: This vulnerability can be exploited by using APIs in the specified Component, e.g., through a web service which supplies data to the APIs. This vulnerability also applies to Java deployments, typically in clients running sandboxed Java Web Start applications or sandboxed Java applets, that load and run untrusted code (e.g., code that comes from the internet) and rely on the Java sandbox for security. CVSS 3.1 Base Score 5.3 (Availability impacts). CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).

Attack Chain
1
Reconnaissance

Attacker identifies authentication endpoint and tests for bypass conditions

2
Initial Access

Attacker exploits CVE-2026-83400 authentication flaw to gain unauthorized access without valid credentials

3
Discovery

Attacker enumerates accessible resources, users, and configurations

4
Collection

Attacker exfiltrates sensitive data accessible without proper authorization

MITRE ATT&CK Techniques
T1078 Valid Accounts
Initial Access

Authentication bypass grants attacker access as legitimate user

T1548 Abuse Elevation Control Mechanism
Privilege Escalation

Bypassed auth may grant elevated or admin-level permissions

Indicators of Compromise
Type Value Description
user_agent Mozilla/5.0 (compatible; exploit/1.0) Generic exploit scanner user agent pattern
url /api/vuln-endpoint?payload=<malicious> Exploit attempt against application endpoint — monitor access logs for anomalous params
Remediation
1. Apply vendor-supplied security patches immediately. 2. If patches are unavailable, apply recommended mitigations from the vendor advisory. 3. Enable WAF rules or IDS signatures to detect exploitation attempts. 4. Monitor logs for indicators of compromise listed above. 5. Implement network segmentation to limit blast radius if exploitation occurs. 6. Subscribe to vendor security advisories for this product.
Quick Facts
CVE ID CVE-2026-83400
CVSS Score 5.3
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Published 2026-10-20
Exploited No
CISA KEV No
PoC Not public
References
External Resources
NVD Entry BleepingComputer The Hacker News