Authelia: Improper Neutralization of Input During Web Page Generation Leads to Potential Cross-site Scripting

Exploitation

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

CVSS 4.0

0.5 · CVSS:4.0/AV:A/AC:H/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:U/S:N/AU:Y/R:U/V:D/RE:L/U:Clear · score source

EPSS

• CVE-2026-33525: 0.24% estimated exploitation activity in the next 30 days; percentile 14.79 (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 Official Weighted Severity Rating: Low This exploit is very unlikely to be the case for most users as it requires configuration of the Content Security Policy template value. Below represents a safe value, any other value other than unconfigured should be very carefully evaluated regardless of the fix. Provided the following conditions are met: 1. The Content Security Policy: 1. Has been disabled or modified from the entirely safe default value; and 2. Has been completely disabled by the Administrator by omitting the header explicitly at the proxy (worst practice); or 3. Has been effectively disabled by modifying script-src allowing unsafe inline scripts rather than using hashes AND effectively disabled by modifying connect-src allowing connections to arbitrary websites. 2. Authelia is being hosted on a domain that has other applications that can write to the cookie for the Authelia domain. 3. One of the other applications noted in 2 has an vulnerability that can be exploited…

Published by the source

24 Mar 2026, 16:33 UTC

Last modified by the source

30 Mar 2026, 14:07 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-gmfg-3v4q-9qr4

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# Patch Next advisory brief: CVE-2026-33525

Advisory: Authelia: Improper Neutralization of Input During Web Page Generation Leads to Potential Cross-site Scripting
IDs: CVE-2026-33525, GHSA-gmfg-3v4q-9qr4
Record: https://patchnext.com/advisories/cve-2026-33525 (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: Low (CVSS 0.5)
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 4.39.16. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/authelia/authelia/v4: affected >= 4.39.15, <= 4.39.15; fixed in 4.39.16

## 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-gmfg-3v4q-9qr4 (GitHub-reviewed advisory GHSA-gmfg-3v4q-9qr4 lists affected ranges: Go github.com/authelia/authelia/v4 >=4.39.15 <=4.39.15)

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