Apache Flink Directory Traversal Vulnerability (CVE-2020-17518/17519) Threat Alert

Apache Flink Directory Traversal Vulnerability (CVE-2020-17518/17519) Threat Alert

janeiro 13, 2021 | Adeline Zhang


Recently, Apache Flink announced two directory traversal vulnerabilities, CVE-2020-17518 and CVE-2020-17519. Currently, Apache Flink has released a new version to fix the preceding vulnerability. Affected users are advised to upgrade as soon as possible.

CVE-2020-17518: Apache Flink 1.5.1 introduced a REST API that allows you to write an uploaded file to an arbitrary location on the local file system, through a maliciously modified HTTP header.

CVE-2020-17519: Apache Flink1.11.0, 1.11.1, and 1.11.2 allow attackers to read any filed on the local file system of the JobManager through the REST interface of the JobManager process. Access is restricted to files accessible by the JobManager process.

The files can be written to any location accessible by Flink 1.5.1. All users should upgrade to Flink 1.11.3 or 1.12.0 if their Flink instance(s) are exposed. The issue was fixed in commit a5264a6f41524afe8ceadf1d8ddc8c80f323ebc4 from apache/flink:master.

Apache Flink is an open-source stream processing framework that can be used for distributed processing of streaming data and is widely used in the field of big data.

Reference link:


Affected Versions


Apache Flink Version: 1.5.1 – 1.11.2


Apache Flink Version: 1.11.0, 1.11.1, 1.11.2

Affected Versions

Apache Flink Version: 1.11.3, 1.12.0


Apache Flink has released new versions to fix the vulnerability. Affected users are advised to upgrade without delay by downloading the updates from the following link:


If related users cannot upgrade Apache Flink for the time being, they can adopt the following measures for temporary protection:

  1.  Make Apache Flink publicly unavailable.
  2.  Add authentication policies for access to Apache Flink.


This advisory is only used to describe a potential risk. NSFOCUS does not provide any commitment or promise on this advisory. NSFOCUS and the author will not bear any liability for any direct and/or indirect consequences and losses caused by transmitting and/or using this advisory. NSFOCUS reserves all the rights to modify and interpret this advisory. Please include this statement paragraph when reproducing or transferring this advisory. Do not modify this advisory, add/delete any information to/from it, or use this advisory for commercial purposes without permission from NSFOCUS.


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