CVE-2026-57898: Unauthenticated File Write in Eclipse BaSyx

How to Detect It

Detection should focus on two linked behaviors: suspicious thumbnail API activity and unexpected file creation by the BaSyx application account. Because the vulnerability involves a crafted fileName parameter, requests containing absolute paths, traversal sequences, Windows drive-letter patterns, or unusual path separators are especially important.

Review HTTP access logs, reverse proxy logs, API gateway telemetry, and application logs for thumbnail upload and retrieval activity. The exact endpoint paths may vary by deployment, so defenders should search broadly for requests referencing thumbnails, AAS resources, and fileName parameters. Pair that with host-based telemetry for file creation events in directories the service account should not normally touch.

If you lack detailed application logging, start with process-centric file monitoring. Any Java process running BaSyx that suddenly writes into cron directories, application startup locations, shell-script directories, temp paths with executable content, or configuration directories deserves immediate review.

Technical Notes

Example log patterns to search for:

fileName=.*(\./|%2e%2e%2f|/etc/|/tmp/|[A-Za-z]:\\)
thumbnail

Example grep against HTTP logs:

grep -E 'thumbnail|fileName=' /var/log/nginx/access.log /var/log/httpd/* 2>/dev/null | 
grep -E '(\./|%2e%2e|/etc/|/tmp/|[A-Za-z]:\\)'

Example Splunk-style query:

index=web (thumbnail OR "fileName=")
| regex _raw="(\./|%2e%2e|/etc/|/tmp/|[A-Za-z]:\\)"
| stats count by src_ip, uri, user_agent

Example Sigma-like hunting logic concept:

title: Suspicious BaSyx Thumbnail Filename Patterns
logsource:
  category: webserver
detection:
  selection1:
    request|contains: "thumbnail"
  selection2:
    request|contains:
      - "fileName=../"
      - "fileName=%2e%2e%2f"
      - "fileName=/etc/"
      - "fileName=/tmp/"
      - "fileName=C:\"
  condition: selection1 and selection2
level: high

Host-level file monitoring example on Linux:

find /tmp /var/tmp /etc /opt /srv -type f -mmin -1440 -ls 2>/dev/null

Mitigation and Patching

The primary remediation is to upgrade Eclipse BaSyx Java Server SDK to 2.0.0-milestone-13 or later. The vulnerable versions are explicitly 2.0.0-milestone-05 through 2.0.0-milestone-12, and the fixed version is explicitly 2.0.0-milestone-13.

If immediate upgrade is not possible, reduce exposure around the AAS thumbnail API and the MongoDB-backed deployment path. Restrict public access to BaSyx endpoints with a reverse proxy, VPN, IP allowlist, or internal-only network policy. If business requirements permit, disable or block thumbnail upload and retrieval routes until the patch is applied. Also review the Java process account and remove unnecessary write permissions from sensitive directories to reduce the odds that file write becomes code execution.

A useful compensating control is to isolate writable directories. If the service account can write only to a controlled data directory and not to startup scripts, config paths, web roots, or scheduler directories, the blast radius is reduced. That is not a fix, but it can materially lower exploit impact while you execute the upgrade.

Technical Notes

Upgrade action depends on how you deploy BaSyx. If you build from source or consume project artifacts, move to 2.0.0-milestone-13 in your dependency or image reference.

Maven example:

<dependency>
  <groupId>org.eclipse.digitaltwin.basyx</groupId>
  <artifactId>basyx-java-server-sdk</artifactId>
  <version>2.0.0-milestone-13</version>
</dependency>

Container image update workflow example:

kubectl set image deployment/basyx-server basyx-server=<your-registry>/<your-image>:2.0.0-milestone-13
kubectl rollout status deployment/basyx-server

Temporary reverse-proxy blocking example for suspicious thumbnail requests in NGINX:

location / {
  if ($args ~* "fileName=(\./|%2e%2e|/etc/|/tmp/|[A-Za-z]:\\)") {
    return 403;
  }
}

Network exposure reduction example:

ufw deny from any to any port 8080 proto tcp
ufw allow from 10.0.0.0/8 to any port 8080 proto tcp

Post-patch validation checklist:

# confirm running version in deployment manifests or build files
grep -Rin "2.0.0-milestone-13" /opt /srv /etc 2>/dev/null

# review recent suspicious files created by the service account
find / -user basyx -type f -mtime -7 2>/dev/null

References

The authoritative public references in the provided research set are the NVD record and Eclipse project resources. The NVD entry contains the core vulnerability description, affected versions, backend-specific condition, and the statement that the issue is fixed in milestone 13. Eclipse project pages help verify repository and release context.

Because some fields remain unknown, practitioners should cite only what is directly supported. In particular, the CVSS score is known, but the vector string was not present in the source data provided. Likewise, no verified public PoC or confirmed in-the-wild exploitation was established from the cited sources.

• NVD CVE entry: https://nvd.nist.gov/vuln/detail/CVE-2026-57898
• Eclipse security work item: https://gitlab.eclipse.org/security/cve-assignment/-/work_items/159
• Eclipse BaSyx GitHub organization: https://github.com/eclipse-basyx
• Eclipse BaSyx Java Server SDK repository: https://github.com/eclipse-basyx/basyx-java-server-sdk
• Eclipse BaSyx Java Server SDK releases: https://github.com/eclipse-basyx/basyx-java-server-sdk/releases

For incident response, defenders should preserve web logs, reverse-proxy logs, process execution telemetry, and file creation records around thumbnail API activity. If suspicious writes are found, treat the host as potentially compromised and scope for follow-on persistence or execution paths.

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