⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● High · CVSS 8.1

How to Fix CVE-2026-40172: Local Privilege Escalation in authentik

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 8.1 - High
Actively exploited?Not currently listed in CISA KEV
Affected< 2025.12.5, >= 2026.2.0-rc1, < 2026.2.3
Fixed ingroups
Type (CWE)CWE-269: Improper Privilege Management

What is CVE-2026-40172?

CVE-2026-40172 is a local privilege escalation flaw in authentik. A local user can abuse the bug to gain higher privileges than they should hold, typically root or SYSTEM. Vendor description: authentik is an open-source identity provider. In versions prior to 2025.12.5 and 2026.2.0-rc1 through 2026.2.2, the PATCH /api/v3/core/users/{pk}/ API allows a caller with change_user on a target user to assign arbitrary groups through UserSerializer, including groups with is_superuser=True, without requiring enable_group_superuser, leading to privilege escalation.

Why this CVE matters

Local privilege escalation flaws are a building block for the broader attack chain. They turn a low-privileged foothold, often gained through phishing or an unrelated web exploit, into full host control.

For deployments of authentik that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open authentik's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-40172

  1. Read the vendor advisory in full: https://github.com/goauthentik/authentik/security/advisories/GHSA-h6x7-hjjc-wjc9
  2. Upgrade authentik to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

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Patch via your OS package manager

Vendor advisory (always check this first for exact fixed version and any

prerequisites): https://github.com/goauthentik/authentik/security/advisories/GHSA-h6x7-hjjc-wjc9


# Vendor advisory: https://github.com/goauthentik/authentik/security/advisories/GHSA-h6x7-hjjc-wjc9
# Debian / Ubuntu: pull the patched build of authentik from your distro repository.
sudo apt update
sudo apt install --only-upgrade authentik

# RHEL / Rocky / AlmaLinux / Fedora
sudo dnf upgrade authentik

# openSUSE
sudo zypper update authentik

# Verify the running version matches the fixed-in version (<patched-version>).
authentik --version || dpkg -s authentik | grep -i version || rpm -q authentik


# Windows: pull the latest cumulative updates that include this CVE's fix.
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck
Import-Module PSWindowsUpdate
Get-WindowsUpdate -AcceptAll -Install -AutoReboot

# If a specific KB is referenced in the advisory, install it directly.
# Get-WindowsUpdate -KBArticleID KBxxxxxxx -AcceptAll -Install -AutoReboot

Verify the fix landed


# Vendor advisory: https://github.com/goauthentik/authentik/security/advisories/GHSA-h6x7-hjjc-wjc9
# 1. Confirm the running version matches the fixed-in version listed above.

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag this CVE on the patched target.

# 3. Inspect recent service / kernel logs for crash-loops or rollback events.
journalctl -u <service> --since "10 minutes ago"
dmesg --since "10 minutes ago"

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If you cannot patch immediately

No official workaround exists beyond restricting network exposure to the affected component. Apply the vendor patch as the primary remediation.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for log entries that do not match your normal request patterns, especially repeated requests to the same uncommon endpoint, and any administrative changes you cannot tie back to a known operator.

Frequently asked questions

Is CVE-2026-40172 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-40172?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for authentik run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*