# CVE-2026-42849: authentik reflected XSS in Simple Flow Executor AutosubmitStage

Source: https://junglewise.ai/threats/cve-2026-42849-authentik-reflected-xss-in-simple-flow-executor-autosubmitstage  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-02. Updated: 2026-06-02  
License: CC BY 4.0 with a link back

CVE-2026-42849 · Severity: critical · CVSS 9.3 · Published 2026-06-02

authentik is an open-source identity provider used to manage user authentication and access to applications. A security flaw in its legacy browser interface allows attackers to execute malicious scripts in a user's browser. This could lead to session hijacking, the theft of sensitive authentication tokens, or unauthorized actions performed on behalf of the user.

Technologies: [Goauthentik Authentik](https://junglewise.ai/threats/technologies/authentik). Vendors: [Goauthentik](https://junglewise.ai/threats/vendors/goauthentik).

## Quick answers

**Is CVE-2026-42849 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-42849 being exploited in the wild.

**How severe is CVE-2026-42849?** Critical severity, with a CVSS score of 9.3, published 2 June 2026.

**Which products and versions are affected?** Goauthentik Authentik < 2025.12.5, < 2026.2.3.

**Is there a fix for CVE-2026-42849?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-42849 attacked?** It is attacked over the network, in a network appliance.

**Am I affected by CVE-2026-42849?** Check whether you run Goauthentik Authentik at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A reflected cross-site scripting (XSS) vulnerability exists in authentik's Simple Flow Executor (SFE), a component designed for legacy browser compatibility. The vulnerability is located in the AutosubmitStage, where the application used jQuery to handle input without explicit sanitization. An attacker can exploit this by leveraging OAuth2 configurations, specifically through the 'state' parameter or a 'redirect_uri' that matches a broad regex. Successful exploitation requires a user to interact with a malicious link, allowing the attacker to execute arbitrary JavaScript in the context of the victim's session, potentially leading to token theft or session hijacking. The issue is resolved in versions 2025.12.5 and 2026.2.3.

## Affected products

- goauthentik authentik < 2025.12.5, < 2026.2.3

## Timeline

- 2026-05-12: advisory: Original GitHub security advisory published
- 2026-06-02: disclosed: CVE published to NVD

## References

- [https://github.com/goauthentik/authentik/security/advisories/GHSA-pgff-5mx8-fqj3](https://github.com/goauthentik/authentik/security/advisories/GHSA-pgff-5mx8-fqj3)

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