What’s Vulnerable › Vulnerabilities
CVE-2020-17518: Apache Flink directory traversal attack: remote file writing through the REST API
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 49.1% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2021-01-05 · updated 2026-06-17
- Weakness: CWE-23
Description
Apache Flink 1.5.1 introduced a REST handler that allows you to write an uploaded file to an arbitrary location on the local file system, through a maliciously modified HTTP HEADER. 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.
Affected products
- Apache Software Foundation Apache Flink: from 1.5.1 before 1.11.3 — fixed in 1.11.3
How to fix
Upgrade to a fixed version: Apache Software Foundation Apache Flink 1.11.3. Check the vendor advisory for mitigations.
References
- http://www.openwall.com/lists/oss-security/2021/01/05/1
- https://lists.apache.org/thread.html/r0b000dc028616d33cb9aa388eb45d516b789cab0024dad94bc06588a%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r1125f3044a0946d1e7e6f125a6170b58d413ebd4a95157e4608041c7%40%3Cannounce.apache.org%3E
- https://lists.apache.org/thread.html/r229167538863518738e02f4c1c5a8bb34c1d45dadcc97adf6676b0c1%40%3Cdev.flink.apache.org%3E
- https://lists.apache.org/thread.html/r26fcdd4fe288323006253437ebc4dd6fdfadfb5e93465a0e4f68420d%40%3Cuser-zh.flink.apache.org%3E
- https://lists.apache.org/thread.html/r28f17e564950d663e68cc6fe75756012dda62ac623766bb9bc5e7034%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r4a87837518804b31eb9db3048347ed2bb7b46fbaad5844f22a9fd4dc%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r5444acac3407ef6397d6aef1b5aec2db53b4b88ef221e63084c1e5f2%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r705fb2211b82c9f1f8d2b1d4c823bcbca50402ba09b96608ec657efe%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r710693b0d3b229c81f485804ea1145b4edda79c9e77d66c39a0a2ff1%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r7b2ee88c66fc1d0823e66475631f5c3e7f0365204ff0cb094d9f2433%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r8167f30c4c60a11b8d5be3f55537beeda629be61196e693bde403b36%40%3Cissues.flink.apache.org%3E
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