CVE-2020-17519: High Vulnerability in Apache Flink

CVE-2020-17519 is a high-severity vulnerability discovered in Apache Flink that was officially published on January 5, 2021. This vulnerability allows attackers to read any file on the local filesystem of the JobManager through its REST interface. The affected versions include Flink 1.11.0 through 1.11.2, and it is essential for organizations using these versions to upgrade to Flink 1.11.3 or 1.12.0 to mitigate the risk.

The risk to organizations includes potential exposure of sensitive data, as the vulnerability permits unauthorized file access, which can lead to further exploitation or data leakage. Given the nature of this vulnerability and its exploitation status, organizations should prioritize patching immediately.

This vulnerability has been analyzed thoroughly and is currently known to have an exploit available. The potential for it to be actively exploited increases the urgency for organizations to address this flaw promptly.

With a CVSS score of 7.5, this vulnerability is classified as high severity. The implications of this vulnerability underline the necessity for organizations to maintain their Flink instances securely and up-to-date.

Organizations are advised to apply the necessary updates and monitor their systems for any signs of exploitation to safeguard against potential breaches.

Vulnerability Details

The vulnerability arises from a change introduced in Apache Flink 1.11.0, affecting versions 1.11.1 and 1.11.2 as well. It enables attackers to read files accessible to the JobManager process through the REST interface. The issue was rectified in commit b561010b0ee741543c3953306037f00d7a9f0801, and users are encouraged to upgrade to Flink 1.11.3 or 1.12.0.

The vulnerability is classified under CWE-552, indicating improper access control, and highlights the need for robust security measures in software environments.

The CVSS score for this vulnerability is 7.5, signifying a high level of severity due to its potential impact on confidentiality, while integrity and availability impacts remain unaffected.

The vulnerability was first published on January 5, 2021, and organizations should be aware that the effective mitigation requires upgrading to the recommended versions as soon as possible.

Technical Analysis

The root cause of CVE-2020-17519 lies in the improper validation of access controls within the REST interface of the JobManager process. Attackers can exploit this weakness to access files on the local filesystem, including potentially sensitive information.

The attack vector is network-based, allowing unauthorized users to interact with the REST API without requiring any prior authentication. The attack complexity is classified as low, as no special conditions are required for exploitation.

No privileges are required for an attacker to leverage this vulnerability, and there is no user interaction needed. The confidentiality impact is high, as sensitive files can be read, while integrity and availability impacts are non-existent.

Risk & Impact Analysis

The real-world impact of this vulnerability could be significant. Organizations that expose their Flink instances to the internet may inadvertently allow attackers to read sensitive files stored on the JobManager's local filesystem. This could lead to data breaches and loss of sensitive information, which can have severe repercussions for organizational integrity and trust.

The blast radius potential is considerable, as attackers could exploit this vulnerability to gain access to critical configurations or sensitive data stored by the application. Given its high CVSS score, organizations must prioritize remediation efforts based on the severity of this vulnerability.

As this vulnerability is listed in the Known Exploited Vulnerabilities (KEV) catalog, organizations should act swiftly to mitigate the risks associated with it. The urgency for remediation is critical, especially for those who have yet to apply the necessary updates.

Exploitation Status

Affected Versions

Apache Flink versions 1.11.0 through 1.11.2 are affected by this vulnerability. Users are advised to upgrade to Flink 1.11.3 or 1.12.0 to mitigate the risks associated with this vulnerability.

Mitigation & Remediation

To mitigate the risks associated with CVE-2020-17519, organizations should upgrade their Flink instances to version 1.11.3 or 1.12.0. If an immediate upgrade is not feasible, organizations should review their network configurations to restrict access to the JobManager REST interface.

Additionally, implementing network controls to limit exposure and monitoring for suspicious activity around the JobManager can help mitigate potential exploitation. For continuous security and validation, organizations should consider investing in continuous security testing to identify any weaknesses.

Detection Guidance

Organizations should monitor logs for unusual access patterns to the JobManager REST interface, which could indicate attempts to exploit CVE-2020-17519. Behavioral anomalies in file access or unexpected API calls should also be flagged for further investigation.

AppSecure Threat Intelligence Insight

The long-term significance of CVE-2020-17519 highlights the importance of proper access controls in web applications. This vulnerability serves as a reminder for security teams to regularly review their configurations and ensure that sensitive components are not exposed unnecessarily.

This incident represents a broader trend in vulnerabilities related to improper access control, which can lead to data breaches. Organizations should implement robust security measures and regularly assess their infrastructures to prevent such vulnerabilities from arising.

Security teams can learn from this vulnerability by emphasizing the need for regular audits and updating their security policies. For further reading on effective security practices, consider reviewing our resources on penetration testing methodology and vulnerability management program design to strengthen your defenses.