The recently identified vulnerability in Jenkins, designated as CVE-2026-27099, affects Jenkins versions 2.483 through 2.550, as well as LTS versions 2.492.1 through 2.541.1. This vulnerability allows for a stored cross-site scripting (XSS) attack due to improper escaping of user-provided descriptions for the 'Mark temporarily offline' cause. Attackers with Agent/Configure or Agent/Disconnect permissions can exploit this vulnerability.
With a CVSS score of 8.0, this vulnerability is classified as high severity, indicating a significant risk to organizations using affected versions of Jenkins. The implications of this flaw are serious, as successful exploitation could lead to unauthorized actions and data exposure.
Given the potential for exploitation, organizations using vulnerable Jenkins versions should prioritize patching these systems immediately. The risk to organizations includes potential data breaches and unauthorized access to sensitive information.
As of now, there is no public exploit confirmed or available for this vulnerability, but the nature of the XSS vulnerability warrants immediate attention from security teams.
Organizations should address this issue in their priority patch cycle to mitigate risks associated with this vulnerability.
Vulnerability Details
The vulnerability allows attackers to inject malicious scripts into the Jenkins application, which can then be executed in the context of users interacting with the application. The official CVE description states that Jenkins versions 2.483 through 2.550, and LTS versions 2.492.1 through 2.541.1 are affected due to improper escaping of user-provided descriptions.
The CVSS score of 8.0 reflects high severity, indicating that the vulnerability poses a significant threat. The attack vector is classified as NETWORK, with low attack complexity and low privileges required for exploitation. User interaction is required for successful exploitation, and impacts include high confidentiality, integrity, and availability.
The weakness has been classified under CWE-79, which addresses improper neutralization of input during web page generation (XSS).
Technical Analysis
The root cause of this vulnerability lies in the failure to properly escape user inputs that are rendered back to the web application. The attack vector is network-based, allowing attackers to exploit the vulnerability remotely without needing physical access to the system.
The attack complexity is low, meaning that attackers do not require advanced skills to exploit this vulnerability. Privileges required for exploitation are also low, as users with Agent/Configure or Agent/Disconnect permissions can initiate the attack. User interaction is necessary, as the XSS payload must be executed by another user's web browser.
The impact on confidentiality, integrity, and availability is high, as successful exploitation can lead to unauthorized access to sensitive information, manipulation of data, and disruption of services.
Risk & Impact Analysis
The real-world risk associated with CVE-2026-27099 is significant. Organizations utilizing vulnerable versions of Jenkins are at risk of data breaches, unauthorized access, and potential system compromises. The blast radius of this vulnerability could extend beyond the initial target, affecting other interconnected systems and services.
Given its high CVSS score, the urgency for organizations to remediate this vulnerability is critical. Organizations should prioritize patching affected Jenkins installations immediately to mitigate the risk of exploitation.
Failure to address this vulnerability could lead to severe financial and reputational damage, particularly if sensitive data is compromised.
Exploitation Status
Signal | Status |
|---|---|
Known Exploit | No |
Public PoC | No |
Actively Exploited | No |
Ransomware Use | No |
Affected Versions
The following versions of Jenkins are affected by this vulnerability: Jenkins 2.483 through 2.550 (inclusive) and LTS 2.492.1 through 2.541.1 (inclusive). Organizations using these versions should take immediate action to patch their systems.
Mitigation & Remediation
Organizations should prioritize patching affected Jenkins installations. The recommended version to upgrade to is the latest stable release beyond 2.550. In addition to patching, organizations should review their configurations and implement security measures such as input validation and sanitization.
For continuous security, organizations should consider utilizing continuous security testing to identify potential weaknesses in their applications.
Detection Guidance
To detect potential exploitation of this vulnerability, organizations should monitor their logs for indicators of XSS attacks, unusual user interactions, and any unauthorized changes made in Jenkins. Behavioral anomalies in user sessions should also be investigated, and network signatures should be put in place to detect suspicious activity.
AppSecure Threat Intelligence Insight
CVE-2026-27099 highlights the importance of input validation and escaping techniques in web applications. Organizations can learn from this vulnerability to enhance their security posture and prevent similar issues in the future. It underscores the necessity for regular security assessments and penetration testing to validate their defenses.
Organizations are encouraged to maintain an updated vulnerability management program to effectively respond to emerging threats. By incorporating lessons learned from vulnerabilities such as CVE-2026-27099, security teams can strengthen their defenses and reduce the risk of exploitation.
For comprehensive security strategies, organizations should also consider adopting frameworks like vulnerability management programs to manage their security risks effectively.
Finally, organizations should remain vigilant and stay informed about the latest security threats and vulnerabilities to ensure they can respond promptly to any emerging risks.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
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