CVE-2025-53864: Medium Vulnerability in Connect2id Nimbus JOSE + JWT

CVE-2025-53864 is a medium-severity vulnerability that affects Connect2id Nimbus JOSE + JWT versions 10.0.x prior to 10.0.2 and 9.37.x prior to 9.37.4. This vulnerability allows a remote attacker to cause a denial of service by supplying a deeply nested JSON object in a JWT claim set due to uncontrolled recursion. The severity of this vulnerability is classified with a CVSS score of 5.8, indicating that while it may not be the most critical threat, it poses a significant risk to affected systems.

Risk to organizations includes potential downtime caused by denial of service, which can disrupt operations and access to services. Given that this vulnerability is independent of the Gson 2.11.0 issue, it highlights the importance of validating input depth, which could have been implemented in the Connect2id product itself.

Organizations should prioritize patching immediately, as failure to address this vulnerability can lead to significant service interruptions. It is crucial for security teams to monitor for potential exploits and ensure that they are protected against this vulnerability.

As of now, there are no known exploits for this vulnerability, and it has not been classified as actively exploited in the wild. However, the possibility of future attacks requires vigilance from security professionals.

Vulnerability Details

The official description of CVE-2025-53864 indicates that the vulnerability allows a remote attacker to cause a denial of service via a deeply nested JSON object supplied in a JWT claim set. This issue arises due to uncontrolled recursion, which can lead to application crashes or excessive resource consumption.

The CVSS score for this vulnerability is 5.8, indicating a medium severity level. The scoring indicates that the attack vector is network-based, requiring low complexity to exploit, and does not require any privileges or user interaction. The impact on availability is low, while confidentiality and integrity are unaffected.

The affected versions are those prior to 10.0.2 and 9.37.4 of the Connect2id Nimbus JOSE + JWT software, published on July 11, 2025. The vulnerability is classified under CWE-674, which relates to insufficient control of a resource through its lifetime.

Technical Analysis

The root cause of this vulnerability lies in the handling of deeply nested JSON objects within JWT claims. When a remote attacker supplies a JSON object with excessive depth, the application can enter uncontrolled recursion, leading to a denial of service.

The attack vector is network-based, which means that an attacker can exploit this vulnerability over the internet without requiring physical access to the system. The complexity to execute such an attack is low, as it does not require any privileges or user interaction.

The vulnerability's impact on availability is classified as low. Since the uncontrolled recursion can lead to service crashes, organizations may experience downtime, affecting users and potentially causing financial losses.

In terms of confidentiality and integrity, there is no impact. However, the risk of service disruption necessitates organizations to take immediate action to mitigate this vulnerability.

Risk & Impact Analysis

Real-world deployment of this vulnerability can lead to significant risks for organizations reliant on Connect2id Nimbus JOSE + JWT for handling JWT claims. A successful attack can disrupt services and degrade the user experience, leading to potential financial repercussions and damage to reputation.

The blast radius of this vulnerability could be substantial, especially for applications that heavily rely on JWT for authentication and authorization. Given the nature of the attack, exploitation can be achieved with minimal effort, increasing the urgency for organizations to address this vulnerability.

Organizations should assess the risk based on the CVSS score of 5.8, indicating a medium level of severity. The lack of known exploits currently minimizes immediate risk, but the potential for future exploitation remains a concern. Continuous monitoring and rapid response are essential.

Affected Versions

The specific affected versions of Connect2id Nimbus JOSE + JWT are all versions prior to 10.0.2 and 9.37.4. Organizations using these versions should be aware and take action to mitigate this vulnerability.

Mitigation & Remediation

To mitigate this vulnerability, organizations should upgrade to Connect2id Nimbus JOSE + JWT version 10.0.2 or 9.37.4 and apply any available security patches. In cases where an immediate upgrade is not possible, consider implementing JSON object depth limits to prevent deeply nested claims.

Additionally, organizations are encouraged to conduct regular security assessments to identify any weaknesses within their systems. Continuous monitoring for unusual activity and potential denial of service attempts should also be part of the security strategy.

For further insights into security practices, organizations can refer to our penetration testing services.

Detection Guidance

Organizations should monitor logs for any signs of excessive recursion or denial of service attempts. Behavioral anomalies, such as significant drops in service performance or unavailability, should prompt further investigation.

Network signatures that can identify suspicious JSON payloads may also aid in detecting potential exploitation attempts.

AppSecure Threat Intelligence Insight

The long-term significance of CVE-2025-53864 lies in its demonstration of how input handling vulnerabilities can lead to severe service disruptions. This highlights the need for organizations to implement robust validation mechanisms within their applications.

As a trend, this vulnerability reflects a pattern where developers may overlook nested input validation, leading to potential denial of service scenarios. Security teams should learn from this incident to enhance their development and security practices.

For more information on improving application security, organizations should explore our resources on penetration testing methodology and vulnerability management program design to bolster their defenses.

Ultimately, the strategic takeaway from this vulnerability is the importance of proactive measures in application security, reinforcing the need for ongoing vigilance and assessment.