goshs has an empty-username SFTP password authentication bypass

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-40884: 0.48% estimated exploitation activity in the next 30 days; percentile 41.32 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary goshs contains an SFTP authentication bypass when the documented empty-username basic-auth syntax is used. If the server is started with -b ':pass' together with -sftp, goshs accepts that configuration but does not install any SFTP password handler. As a result, an unauthenticated network attacker can connect to the SFTP service and access files without a password. I reproduced this on the latest release v2.0.0-beta.5. Details The help text explicitly documents empty usernames as valid authentication input: - options/options.go:264-266 says Use basic authentication (user:pass - user can be empty) The SFTP sanity check only requires that either -b or --sftp-keyfile is present: That parsing logic then splits -b ':pass' into an empty username and a non-empty password: But the SFTP server only installs a password handler if both the username and password are non-empty: With -b ':pass', that condition is false, so no password authentication is enforced for SFTP sessions. Relevant…

Published by the source

14 Apr 2026, 22:28 UTC

Last modified by the source

27 Apr 2026, 16:17 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-c29w-qq4m-2gcv

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# Patch Next advisory brief: CVE-2026-40884

Advisory: goshs has an empty-username SFTP password authentication bypass
IDs: CVE-2026-40884, GHSA-c29w-qq4m-2gcv
Record: https://patchnext.com/advisories/cve-2026-40884 (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Partial vendor fix; fixed versions by package: github.com/patrickhener/goshs/v2 2.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/patrickhener/goshs/v2: affected < 2.0.0; fixed in 2.0.0
- Go github.com/patrickhener/goshs: affected <= 1.1.4

## Suggested inspection (read-only)
- Go github.com/patrickhener/goshs/v2: check the installed version with your package manager.
- Go github.com/patrickhener/goshs: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/patrickhener/goshs/v2, github.com/patrickhener/goshs.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-c29w-qq4m-2gcv (GitHub-reviewed advisory GHSA-c29w-qq4m-2gcv lists affected ranges: Go github.com/patrickhener/goshs >=0 =0 <2.0.0)

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