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Critical

XSS in authentik AutosubmitStage

IdentifiersCVE-2026-42849CWE-79· Improper Neutralization of Input…

CVE-2026-42849 is a cross-site scripting vulnerability in authentik, an open-source identity provider. The flaw affects versions prior to 2025.12.5 and 2026.2.3 and is specifically associated with the AutosubmitStage component. According to the advisory, the issue was introduced by the implementation of stages in the Simple Flow Executor (SFE) to improve compatibility with legacy browsers, which made it possible to exploit an XSS condition in AutosubmitStage.

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Are you exposed to this one?

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows attacker-controlled script to execute in a victim's browser in the context of the authentik application. Based on the provided CVSS vector (AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N), the issue can lead to high confidentiality and integrity impact, including theft of session data or other sensitive information exposed to the browser, execution of actions as the victim within the application, and manipulation of application content or workflow state. No direct availability impact is indicated.

Mitigation

If you can’t patch tonight, do this now.

If immediate patching is not possible, reduce exposure to vulnerable AutosubmitStage flows where feasible and limit opportunities for untrusted input to reach affected authentication flows. Standard XSS hardening measures such as strict output encoding, stronger content security policy, and minimizing use of legacy-browser compatibility behaviors may reduce risk, but the authoritative fix is to upgrade to 2025.12.5 or 2026.2.3.

Remediation

Patch, then assume compromise.

Upgrade authentik to a fixed release. The issue is patched in versions 2025.12.5 and 2026.2.3. Systems running versions prior to those releases should be updated to the appropriate patched version branch.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType
GoauthentikAuthentikapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.
Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity5

Community discussion across Reddit, Mastodon, and other social sources.