CVE-2020-17518: Apache Flink directory traversal attack: remote file writing through the REST API
- Is it exploited?
Reported, not confirmed by CISA. VulnCheck KEV lists it as exploited in the wild. CISA has not added it to its Known Exploited Vulnerabilities catalog as of .
VulnCheck KEV lists it since . It cites 555 public reports, the first from .
- How likely is exploitation in the next 30 days?
- 49.1%
EPSS score, percentile 98.9 of all scored records. A probability estimated by FIRST, not a report of exploitation.
- How severe?
- Not scored
The CVE record carries no CVSS score.
- What should I do?
CISA has set no required action, because the vulnerability is not in KEV.
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- Apache Flink 1.5.1 to 1.11.2
Source: CISA KEV 2026.10.29, as of ; VulnCheck KEV, as of ; FIRST EPSS, as of ; CVE List, as of . About the data.
Description
Apache Flink directory traversal attack: remote file writing through the REST API
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.
Source: CVE List, as of . About the data.
What to do
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
This summary is based on the CVE record as of . Check the vendor's advisory before you act: affected versions and fixes can change.
Affected products and versions
Versions by product, as listed in the CVE record (1 product)
| Status | Versions |
|---|---|
| Affected | Apache Flink 1.5.1 to 1.11.2 |
Source: CVE List, as of . About the data.
Weakness
CWE-23
- CWE-23: Relative Path Traversal
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| CVE record last updated |
References
24
- lists.apache.org
- [flink-user] 20210105 [CVE-2020-17518] Apache Flink directory traversal attack: remote file writing through the REST API
- [announce] 20210105 [CVE-2020-17518] Apache Flink directory traversal attack: remote file writing through the REST API
- [oss-security] 20210105 [CVE-2020-17518] Apache Flink directory traversal attack: remote file writing through the REST API
- [flink-issues] 20210106 [GitHub] [flink-web] zentol commented on a change in pull request #408: Add security page for Flink
- [flink-dev] 20210106 [jira] [Created] (FLINK-20875) Could patch CVE-2020-17518 to version 1.10
- [flink-issues] 20210106 [jira] [Created] (FLINK-20875) Could patch CVE-2020-17518 to version 1.10
- [flink-issues] 20210107 [jira] [Updated] (FLINK-20875) Could patch CVE-2020-17518 to version 1.10
- [flink-issues] 20210107 [jira] [Closed] (FLINK-20875) Could patch CVE-2020-17518 to version 1.10
- [flink-issues] 20210107 [jira] [Commented] (FLINK-20875) Could patch CVE-2020-17518 to version 1.10
- [flink-issues] 20210112 [jira] [Commented] (FLINK-20875) Could patch CVE-2020-17518 to version 1.10
- [flink-dev] 20210113 Re: [DISCUSS] Releasing Apache Flink 1.10.3
12 more in the CVE record.
Known exploited Apache vulnerabilities
- CVE-2016-3081: Apache Struts Command Injection Vulnerability
- CVE-2026-34486: Apache Tomcat Missing Encryption of Sensitive Data Vulnerability
- CVE-2026-34197: Apache ActiveMQ Improper Input Validation Vulnerability
- CVE-2024-38475: Apache HTTP Server Improper Escaping of Output Vulnerability
- CVE-2025-24813: Apache Tomcat Path Equivalence Vulnerability