CVE-2026-57294: Jenkins EC2 Fleet Plugin Credential Exposure via Missing Permission Check

Technical summary

CVE-2026-57294 is a privilege boundary violation in the Jenkins EC2 Fleet Plugin caused by insufficient authorization checks. The vulnerability allows a user with only Overall/Read permission to initiate connections to attacker-controlled endpoints while supplying credential identifiers. The plugin fails to validate whether the requesting user has permission to use those credentials, creating a path for an already-authenticated attacker to exfiltrate AWS secrets. The CVSS 3.1 score of 5.4 (MEDIUM) reflects a low-barrier attack requiring only low-privilege credentials and basic network access, with confidentiality and integrity impacts but no availability component.

Business impact

For organizations using Jenkins EC2 Fleet Plugin in AWS environments, this vulnerability creates insider-threat and lateral-movement risk. A compromised Jenkins user account or an insider with minimal Jenkins permissions can pivot to AWS credential theft, potentially gaining unauthorized cloud infrastructure access. This is particularly concerning in multi-tenant Jenkins deployments or where Jenkins serves as a secrets store. Remediation delays extend the window for undetected credential exfiltration.

Affected systems

The vulnerability impacts Jenkins EC2 Fleet Plugin version 4.2.3.539.v8fedff2a_81c3 and all earlier versions. Any Jenkins instance running this plugin with users granted Overall/Read permission is potentially exposed. Organizations should verify their installed plugin version via Manage Jenkins > Manage Plugins.

Exploitability

Exploitation requires an attacker to already possess Jenkins access credentials (Overall/Read privilege minimum) and to have obtained AWS credential IDs through a separate method—such as configuration disclosure, logs, or prior reconnaissance. The attack itself is straightforward and requires no user interaction or specialized tools. The CVSS vector AV:N/AC:L/PR:L reflects network-based exploitation with low complexity, making it practical for motivated threat actors.

Remediation

Upgrade Jenkins EC2 Fleet Plugin to a patched version released after the 4.2.3.539.v8fedff2a_81c3 release. Verify the update through the Jenkins plugin manager. Additionally, apply principle-of-least-privilege access controls: restrict Overall/Read permissions to trusted users only, and consider isolating Jenkins credential stores using role-based access controls and Jenkins' native authorization strategies (e.g., Matrix-based authorization).

Patch guidance

Consult the official Jenkins EC2 Fleet Plugin release notes and security advisory for the specific patched version number. Updates are available through the Jenkins plugin manager (Manage Jenkins > Manage Plugins > Updates). Test updates in a non-production environment first to ensure compatibility with existing job configurations and cloud provider integrations.

Detection guidance

Monitor Jenkins audit logs for Overall/Read-level users initiating EC2 Fleet Plugin connections to unexpected external hosts. Review Jenkins credentials configuration history for unauthorized access attempts. AWS CloudTrail logs may reveal whether any exposed credentials were actually used to make cloud API calls. Inspect EC2 Fleet Plugin logs for connection attempts to non-standard endpoints.

Why prioritize this

Although the CVSS score is MEDIUM, prioritize remediation in multi-user Jenkins environments, especially those managing sensitive AWS infrastructure or handling secrets. This is not a critical remote-code-execution or unauthenticated-access flaw, but the combination of low-barrier exploitation, credential exposure, and cloud infrastructure impact warrants prompt patching before widespread adoption of the vulnerable version.

Risk score, explained

The CVSS 3.1 score of 5.4 reflects a low-complexity, network-accessible vulnerability requiring low-privilege authentication. Confidentiality (AWS credential disclosure) and integrity (potential for credential misuse) impacts are acknowledged. The lack of availability impact and the requirement for prior knowledge of credential IDs (not auto-enumerated) prevents a higher severity rating. In practice, organizational risk depends on Jenkins exposure, user privilege distribution, and the sensitivity of stored credentials.

Frequently asked questions