CVE-2026-61503

MEDIUM 5.3

Rejetto HFS < 3.2.1 Username Enumeration via Login Response Differences

CVSS Score

5.3

EPSS Score

0.3%

EPSS Percentile

27th

Rejetto HFS 3.0.0 through 3.2.0 returns observably different responses from its login endpoint depending on whether the submitted username exists. A remote unauthenticated attacker can use this to confirm valid account names, including the default admin account, facilitating password-guessing and session-forgery attacks.

CWE	CWE-204
Vendor	rejetto
Product	hfs
Published	Jul 13, 2026
Last Updated	Jul 15, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Affected Versions

rejetto / hfs

3.0.0 < 3.2.1

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/rejetto/hfs/releases/tag/v3.2.1 vulncheck.com: https://www.vulncheck.com/advisories/rejetto-hfs-username-enumeration-via-login-response-differences

Credits

Zach Hanley (@hacks_zach) of Horizon3.ai, in collaboration with Claude and Anthropic Research