# CVE-2026-126239: CVE-2026-126239

Status: published. Published: 2026-11-11. Updated: 2026-11-11.

A stack-based buffer overflow vulnerability in Fortinet FortiAuthenticator 8.0.0 through 8.0.3, FortiAuthenticator 6.6.0 through 6.6.10 may allow an unauthenticated attacker to crash the FSSO subsystem via crafted http requests

## Remediation

- fix: Upgrade to FortiAuthenticator version 8.0.4 or above
Upgrade to FortiAuthenticator version 6.6.11 or above (source: CNA: fortinet)

## Affected products and versions

- Fortinet / FortiAuthenticator: ≥ 8.0.0; ≤ 8.0.3 (affected, semver); ≥ 6.6.0; ≤ 6.6.10 (affected, semver). Source: CNA: fortinet

## Severity and prioritization

- CVSS 3.1: 7.5 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:P/RL:O/RC:C; source: CNA: fortinet

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-121

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://fortiguard.fortinet.com/psirt/FG-IR-26-254 (CNA: fortinet)

## Provenance

- CNA: fortinet: https://www.cve.org/CVERecord?id=CVE-2026-126239; retrieved 2026-11-11; source updated 2026-11-11

Revision: 2540bca7b27f98447090be0a41cbb84350f13791400df16ec618e63a4e584f1d

Canonical: https://y2.dev/cve/CVE-2026-126239

## Agent and API access

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- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.