# CVE-2026-59104: UgCS server HCI authentication bypass with empty credentials

Status: published. Published: 2026-11-06. Updated: 2026-11-06.

UgCS server before 6.2 contains an authentication bypass in the HCI protocol login handler (LoginHandler) exposed on TCP port 3334. When the user database contains exactly one user (the default single-operator installation), a LoginRequest with empty userLogin and userPassword fields is interpreted as \"use the only user\" rather than as invalid credentials, and the server returns a fully authenticated session. Because the service listens on all interfaces (0.0.0.0) without TLS by default, an unauthenticated remote attacker with network access to port 3334 can obtain an authenticated session without knowing any credential and then issue privileged commands, including commanding connected drones and uploading flight routes.

## Remediation

- fix: Upgrade to UgCS 6.2 or later, in which empty credentials are no longer accepted as a valid login. (source: CNA: ENISA)
- workaround: For deployments that cannot upgrade immediately: bind the HCI listener to 127.0.0.1, restrict TCP port 3334 with host and network firewall rules, and place the service behind an authenticated TLS transport. (source: CNA: ENISA)

## Affected products and versions

- SPH Engineering / UgCS: ≥ 0; < 6.2 (affected, custom). Source: CNA: ENISA; platforms: Windows, MacOS, Linux

## Severity and prioritization

- CVSS 4.0: 9.3 (critical); CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: ENISA

- CVSS 3.1: 9.8 (critical); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H; source: CNA: ENISA

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-287

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://www.ugcs.com/ (CNA: ENISA; product)

- https://offseq.com/en/research/ugcs-cve-2026-59104/ (CNA: ENISA; third-party-advisory)

## Provenance

- CNA: ENISA: https://www.cve.org/CVERecord?id=CVE-2026-59104; retrieved 2026-11-06; source updated 2026-11-06

Revision: 36930f940f4f9f1200ded0c32dd6c270a87f3c571c5b266fb373afd0b187ed50

Canonical: https://y2.dev/cve/CVE-2026-59104

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