---
id: "CVE-2026-126254"
page: "https://infrastack.ai/live/CVE-2026-126254"
kind: "vulnerability"
aliases: ["CVE-2026-126254"]
title: "FortiOS: numeric truncation lets a BGP neighbor send malformed routes"
severity: "critical"
cvss: 9.6
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["bgp", "firewalls", "fortinet", "fortios", "infrastructure", "routers"]
not_affected_if: ["fortios-outside-listed-ranges", "no-bgp", "no-ibgp-neighbors"]
published_at: "2026-11-11T22:17:25+00:00"
first_seen_at: "2026-11-11T22:29:33+00:00"
updated_at: "2026-11-11T22:31:02+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-126254", "first_seen_at": "2026-11-11T22:29:33+00:00"}]
exploit_sources: []
---

# FortiOS: numeric truncation lets a BGP neighbor send malformed routes

Link for people: https://infrastack.ai/live/CVE-2026-126254 (this .md is for agents)

FortiOS, Fortinet's firewall and router operating system, mishandles numeric values in BGP attributes. A configured iBGP neighbor can send specially crafted malformed attributes that reach every router connected to it.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check the installed FortiOS version in the admin interface or with `get system status`
- Check whether BGP is configured with `get router info bgp summary` and list the iBGP neighbors

## Fix

- Move to a fixed FortiOS release listed in the Fortinet advisory; the sources do not name the fixed versions

## Timeline

- 2026-11-11T22:29:33+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-126254

## From the sources

A numeric truncation error vulnerability in Fortinet FortiOS 8.0.0 through 8.0.1, FortiOS 7.6.0 through 7.6.7, FortiOS 7.4.0 through 7.4.12, FortiOS 7.2.0 through 7.2.13 may allow a configured ibgp neighbor to send malicious/malformed attributes to all connected routers via a specially crafted request

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_