CVE-2026-54734

CRITICAL CVSS 10.0 PoC Available
Published: 2026-09-17
Modified: 2026-09-18
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AI Threat Summary

CVE-2026-54734 is a critical vulnerability with a CVSS score of 10.0 affecting the target software. Threat hunters should monitor for exploit attempts and apply vendor patches immediately.

Description

Prebid Server Java is the Java version of Prebid Server. Prior to 3.43.0, certain bidder adapters interpolate user-supplied parameters into outbound request URLs without using HttpUtil to validate the resulting domain or path segment. A malicious actor who can supply bid-request parameters can cause the server to send HTTP requests to unintended destinations, potentially reaching internal network services, metadata endpoints, or other sensitive server endpoints with the server's network access. This issue is fixed in version 3.43.0.

Attack Chain
1
Reconnaissance

Attacker scans for vulnerable versions using version banners or PoC scanners

2
Initial Access

Attacker triggers CVE-2026-54734 vulnerability with a crafted request or payload

3
Execution

Vulnerability exploited to perform unauthorized actions on the target system

4
Impact

Depending on vulnerability type, attacker achieves data access, service disruption, or code execution

MITRE ATT&CK Techniques
T1190 Exploit Public-Facing Application
Initial Access

Public-facing application vulnerability exploited for initial access

T1203 Exploitation for Client Execution
Execution

Vulnerability exploited to execute attacker-controlled code

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-2026-54734
CVSS Score 10.0
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Published 2026-09-17
Exploited No
CISA KEV No
PoC Available
References
External Resources
NVD Entry BleepingComputer The Hacker News