High-severity RCE in a widely used enterprise file-transfer product (WS_FTP Server) that can lead to full server compromise and data loss; worth broad IT distribution.
CVE-2026-90866
Path traversal in WS_FTP Server allows delegated admin to escape scope and enable RCE.
Is CVE-2026-90866 being exploited?
Not confirmed. CVE-2026-90866 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked.
How severe is CVE-2026-90866?
CVE-2026-90866 is rated Critical with a CVSS score of 9.1. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-90866?
Yes. A fix has been recorded for CVE-2026-90866. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-90866 affect?
CVE-2026-90866 affects Progress WS_FTP Server (Windows) versions prior to 2024.0.7, Progress WS_FTP Server (Windows) versions prior to 2025.0.4, Windows servers running affected WS_FTP Server builds. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-90866?
Patch immediately to 2024.0.7/2025.0.4 and restrict delegated Host Administrator access.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Delegated Host Administrator can traverse filesystem to access/modify arbitrary files and achieve remote code execution on WS_FTP Windows servers.
Immediate action required
- affected< 2024.0.7
- affected< 2025.0.4
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.