Authelia Missing Username Canonicalization in Basic Auth (LDAP)

Exploitation

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

CVSS 4.0

2.9 · CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/CR:L/IR:L/AR:L/MAV:N/MAC:H/MAT:N/MPR:N/MUI:N/MVC:L/MVI:N/MVA:N/MSC:N/MSI:N/MSA:N/S:N/AU:Y/R:U/V:D/RE:L/U:Green · score source

EPSS

• CVE-2026-47203: 0.45% estimated exploitation activity in the next 30 days; percentile 39.36 (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.

Impact CVSSv4 Baseline Score: Moderate 6.3 CVSSv4 Weighted Score: Low 2.9 The full CVSSv4 Vector for this vulnerability is: CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/CR:L/IR:L/AR:L/MAV:N/MAC:H/MAT:N/MPR:N/MUI:N/MVC:L/MVI:N/MVA:N/MSC:N/MSI:N/MSA:N/S:N/AU:Y/R:U/V:D/RE:L/U:Green CVSSv3.1 Baseline Score: Low 3.7 CVSSv3.1 Overall Score: Medium 4.0 The full CVSSv3.1 Vector equivalent for this vulnerability is: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N/E:P/RL:O/RC:X/CR:H/IR:L/AR:L/MAV:N/MAC:H/MPR:N/MUI:N/MS:U/MC:L/MI:N/MA:N The weighted severity rating is a result of no indication this is currently being exploited being available at the time of the publish date, in addition to the fact it's unlikely that it is being exploited currently. Due to lack of canonicalization of the basic auth username, the effectiveness of the brute force mechanism when using basic auth is partially degraded. Most passwords of reasonable length are unlikely to have a meaningful effect…

Published by the source

29 May 2026, 21:21 UTC

Last modified by the source

26 Jun 2026, 21:32 UTC

Source last checked

26 Oct 2026, 15:24 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-hjj4-hfjm-fmrj

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# Patch Next advisory brief: CVE-2026-47203

Advisory: Authelia Missing Username Canonicalization in Basic Auth (LDAP)
IDs: CVE-2026-47203, GHSA-hjj4-hfjm-fmrj
Record: https://patchnext.com/advisories/cve-2026-47203 (revision 1, source checked 26 Oct 2026, 15:24 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Low (CVSS 2.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/authelia/authelia/v4 4.39.20. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/authelia/authelia/v4: affected >= 4.38.0, <= 4.39.19; fixed in 4.39.20

## Suggested inspection (read-only)
- Go github.com/authelia/authelia/v4: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/authelia/authelia/v4.
- 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-hjj4-hfjm-fmrj (GitHub-reviewed advisory GHSA-hjj4-hfjm-fmrj lists affected ranges: Go github.com/authelia/authelia/v4 >=4.38.0 <=4.39.19)

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