# CVE-2026-126253: Fortinet FortiOS authentication bypass in OSPF daemon

Source: https://junglewise.ai/threats/cve-2026-126253-a-authentication-bypass-by-primary-weakness-vulnerability-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-11. Updated: 2026-11-11  
License: CC BY 4.0 with a link back

CVE-2026-126253 · Severity: critical · CVSS 9.3 · Published 2026-11-11

FortiOS is a firewall operating system that manages network security and routing protocols. An unauthenticated attacker can bypass authentication in the OSPF routing daemon by sending specially crafted requests, allowing them to broadcast link-state advertisements (LSA) and potentially disrupt or hijack network routing. This could lead to network outages or redirection of traffic through attacker-controlled paths.

Technologies: [Fortinet FortiOS](https://junglewise.ai/threats/technologies/fortios), [Fortinet Fortisase](https://junglewise.ai/threats/technologies/fortisase). Vendors: [Fortinet](https://junglewise.ai/threats/vendors/fortinet).

## Quick answers

**Is CVE-2026-126253 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-126253 being exploited in the wild.

**How severe is CVE-2026-126253?** Critical severity, with a CVSS score of 9.3, published 11 November 2026.

**Which products and versions are affected?** Fortinet FortiOS 8.0.0 through 8.0.1, 7.6.0 through 7.6.7, 7.4.0 through 7.4.12, 7.2.0 through 7.2.13, 7.0.1 through 7.0.19; Fortinet Fortisase 26.3.1, 26.3.1_a, 26.2 all versions, 26.1 all versions, 25.4 all versions, 25.3 all versions, 25.2 all versions, 25.1.a all versions, 25.1 all versions.

**Is there a fix for CVE-2026-126253?** Yes: fixed in FortiOS 8.0.2, 7.6.8, 7.4.13, 7.2.14; FortiSASE 26.3.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-126253 attacked?** It is attacked over the network, in an operating system.

**Am I affected by CVE-2026-126253?** Check whether you run Fortinet FortiOS or Fortinet Fortisase 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.

## How to fix

- Fixed in FortiOS 8.0.2, 7.6.8, 7.4.13, 7.2.14; FortiSASE 26.3.2

## Technical details

An authentication bypass by primary weakness (CWE-305) exists in the OSPF daemon component of FortiOS and FortiSASE. The vulnerability allows an unauthenticated attacker to broadcast LSA messages via specially crafted requests, without proper authentication checks. This is a network-accessible attack requiring no user interaction or prior authentication.

## Affected products

- Fortinet FortiOS 8.0.0 through 8.0.1, 7.6.0 through 7.6.7, 7.4.0 through 7.4.12, 7.2.0 through 7.2.13, 7.0.1 through 7.0.19
- Fortinet FortiSASE 26.3.1, 26.3.1_a, 26.2 all versions, 26.1 all versions, 25.4 all versions, 25.3 all versions, 25.2 all versions, 25.1.a all versions, 25.1 all versions

## Timeline

- 2026-11-10: disclosed

## References

- [https://fortiguard.fortinet.com/psirt/FG-IR-26-267](https://fortiguard.fortinet.com/psirt/FG-IR-26-267)

## Related threats

- [Fortinet FortiOS authentication bypass in HA command execution](https://junglewise.ai/threats/cve-2026-126259-a-missing-authentication-for-critical-function-vulnerability-in)
- [Fortinet FortiOS stack buffer overflow in WAD proxy](https://junglewise.ai/threats/cve-2026-126258-a-stack-based-buffer-overflow-vulnerability-in-fortinet-fortios)
- [Fortinet FortiOS out-of-bounds read in kernel](https://junglewise.ai/threats/cve-2026-126256-a-out-of-bounds-read-vulnerability-in-fortinet-fortios-8-0-0)
- [Fortinet FortiOS path traversal authentication bypass in SSH daemon](https://junglewise.ai/threats/cve-2026-126255-a-path-traversal-filedir-vulnerability-in-fortinet-fortios-8-0-0)
- [Fortinet FortiOS numeric truncation error in BGP daemon](https://junglewise.ai/threats/cve-2026-126254-a-numeric-truncation-error-vulnerability-in-fortinet-fortios-8-0)