Apache Flink Improper Access Control
CVE-2020-17519 is a high-severity files or directories accessible to external parties vulnerability in Apache Flink from Apache, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected Apache Flink versions: Apache Flink 1.11.0 to 1.11.2. The record does not name a fixed version, so check the vendor advisory. CISA added it to the Known Exploited Vulnerabilities catalogue on May 23, 2024, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Check which version of Apache Flink you run against the affected versions below, and install the vendor's latest release.
- CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
- Read the advisory on lists.apache.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache Flink | Apache Flink 1.11.0 to 1.11.2 | Not stated |
| Apache | flink | 1.11.0 through 1.11.2 | Not stated |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- NoneNothing can be modified.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.5 | High | NVD |
| CVSS 3.1 | 9.1 | Critical | CISA (ADP) |
| CVSS 2.0 | 5.0 | Medium | NVD |
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Files or Directories Accessible to External Parties
The product makes files or directories accessible to unauthorized actors, even though they should not be.
How developers prevent this class of flaw
- When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to disable public access.
More Files or Directories Accessible to External Parties vulnerabilities (CWE-552)
Timeline
- CVE record published.
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: partial).
- Deadline for US federal agencies to remediate, set by CISA.
- Record last changed materially (score, affected products, status or references).
References
Advisories
- lists.apache.org/thread.html/r4e1b72bfa789ea5bc20b8afe56119200ed25bdab0eb80d664fa5bfe2%40%3Cdev.flink.apache…Mailing List
- lists.apache.org/thread.html/r6843202556a6d0bce9607ebc02e303f68fc88e9038235598bde3b50d%40%3Cannounce.apache.o…Mailing List
- lists.apache.org/thread.html/r6843202556a6d0bce9607ebc02e303f68fc88e9038235598bde3b50d%40%3Cdev.flink.apache…Mailing List
- lists.apache.org/thread.html/r88b55f3ebf1f8f4e1cc61f030252aaef4b77060b56557a243abb92a1%40%3Cissues.flink.apac…Mailing List
- lists.apache.org/thread.html/r88f427865fb6aa6e6378efe07632a1906b430365e15e3b9621aabe1d%40%3Cissues.flink.apac…Mailing List
Third-party and government advisories
- openwall.com/lists/oss-security/2021/01/05/2Mailing List, Third Party Advisory
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-17519US Government Resource
Technical write-ups (may include proof of concept)
- packetstormsecurity.com/files/160849/Apache-Flink-1.11.0-Arbitrary-File-Read-Directory-Traversal.htmlExploit, Third Party Advisory, VDB Entry
Other references
- lists.apache.org/thread.html/r0a433be10676f4fe97ca423d08f914e0ead341c901216f292d2bbe83%40%3Cissues.flink.apac…Mailing List
- lists.apache.org/thread.html/r1125f3044a0946d1e7e6f125a6170b58d413ebd4a95157e4608041c7%40%3Cannounce.apache.o…Mailing List
- lists.apache.org/thread.html/r229167538863518738e02f4c1c5a8bb34c1d45dadcc97adf6676b0c1%40%3Cdev.flink.apache…Issue Tracking
- lists.apache.org/thread.html/r26fcdd4fe288323006253437ebc4dd6fdfadfb5e93465a0e4f68420d%40%3Cuser-zh.flink.apa…Issue Tracking
- lists.apache.org/thread.html/r28f17e564950d663e68cc6fe75756012dda62ac623766bb9bc5e7034%40%3Cissues.flink.apac…Issue Tracking
- lists.apache.org/thread.html/r2fc60b30557e4a537c2a6293023049bd1c49fd92b518309aa85a0398%40%3Cissues.flink.apac…Issue Tracking
- lists.apache.org/thread.html/r6843202556a6d0bce9607ebc02e303f68fc88e9038235598bde3b50d%40%3Cuser.flink.apache…Issue Tracking
- lists.apache.org/thread.html/r90890afea72a9571d666820b2fe5942a0a5f86be406fa31da3dd0922%40%3Cannounce.apache.o…Mailing List, Not Applicable
- lists.apache.org/thread.html/ra8c96bf3ccb4e491f9ce87ba35f134b4449beb2a38d1ce28fd89001f%40%3Cdev.flink.apache…Issue Tracking
Other vulnerabilities in Apache Flink
- 8.1 High severity
Recent Files or Directories Accessible to External Parties vulnerabilities
- 7.8 High severity
Roundcube Webmail File Disclosure Exploited
- 5.5 Medium severity
ImageMagick Arbitrary File Deletion Exploited
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