CVE-2020-17518
HighExploitedUpload of file to arbitrary path in Apache Flink
Published Feb 9, 2022 · Updated Sep 8, 2026 · Also known as BIT-flink-2020-17518, GHSA-7q5g-gph2-4rc6
Key Facts
Patch immediately- CVE-2020-17518 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting Flink (Apache), org.apache.flink:flink-runtime (maven).
- It is exploited in the wild, listed in Industry KEV feed, CIRCL KEV since Oct 15, 2023. No public exploit code is known.
- EPSS estimates a 51% probability of exploitation in the next 30 days.
- Fixed versions are available, including Flink 1.11.3, org.apache.flink:flink-runtime 1.11.3.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
EPSS (30-day exploit likelihood)
51%
Higher than 98.9% of all scored CVEs
Exploited in the wild
Yes
2 catalog listings
Public exploit code
None known
Get the full CVE-2020-17518 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| Industry KEV feed | Nov 25, 2023 | n/a | Not reported |
| CIRCL KEV | Oct 15, 2023 | n/a | Not reported |
Required action: Apply remediations or mitigations per vendor instructions or discontinue use of the product if remediation or mitigations are unavailable.
Affected Products
5 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| FlinkApache | >= 1.5.1, >= Apache Flink 1.5.1 to 1.11.2 | 1.11.3 |
| org.apache.flink:flink-runtimemaven | >= 1.5.1 | 1.11.3 |
Patched Releases
Flink
1.11.3
org.apache.flink:flink-runtime
1.11.3
Timeline
Publicly disclosed
Feb 9, 2022
Added to CIRCL KEV
Oct 15, 2023
Added to Industry KEV feed
Nov 25, 2023
Last updated
Sep 8, 2026
Weakness Type
- CWE-22 Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
- CWE-23 Relative Path Traversal
References
- advisoryRHSA-2021:3140
- advisoryRHSA-2021:3205
- advisoryRHSA-2021:3207
- advisoryGHSA advisory
- advisory[flink-dev] 20210105 [CVE-2020-17518] Apache Flink directory traversal attack: remote file writing through the REST API
FAQ
Common Questions.
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.
Affected: Flink (Apache) versions >= 1.5.1, >= Apache Flink 1.5.1 to 1.11.2; org.apache.flink:flink-runtime (maven) versions >= 1.5.1. The full list is in the CVE brief.
It is exploited in the wild, listed in Industry KEV feed, CIRCL KEV since Oct 15, 2023.
No, it is not currently listed in the CISA Known Exploited Vulnerabilities catalog.
No public exploit code is known.
Fixed versions are available, including Flink 1.11.3, org.apache.flink:flink-runtime 1.11.3.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
Is CVE-2020-17518 Running On Your Attack Surface?
Brandefense maps vulnerabilities like this one to your internet-facing assets and tells you exactly where to patch.
Request A Demo