CVE
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…
Affects FortiOS 8.0.0-8.0.1, 7.6.0-7.6.7, 7.4.0-7.4.12 and 7.2.0-7.2.13, where a configured iBGP neighbor could send malformed BGP attributes. No fix version is given in the facts.
Written by anthropic/claude-sonnet-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- See vendor advisory
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. FortiOS in an affected version range (8.0.0–8.0.1, 7.6.0–7.6.7, 7.4.0–7.4.12, 7.2.0–7.2.13) The attacker must be a configured iBGP neighbor of the device, handled by the BGP daemon
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 37/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Fortinet FortiOS has a numeric truncation flaw that lets a configured iBGP neighbor send malicious or malformed attributes to all connected routers through a specially crafted request. An attacker can reach it remotely over the network with only low-level privileges and no user interaction, which could let them tamper with routing data and disrupt connected systems.
Read the original description
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
Who should check
Teams running Fortinet FortiOS 7.2, 7.4, 7.6 or 8.0 firewalls (FortiGate) with BGP, where iBGP neighbors are configured. Older FortiSASE releases are also listed as affected.
Read the source excerpt
“A Numeric Truncation Error vulnerability [cwe-197] in FortiOS and FortiSASE bgp daemon may allow a configured ibgp neighbor to send malicious/malformed attributes”
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure8/25Specific setups only, reachable over the network
- Reach14/20Affects Fortinet (an enterprise product or network appliance)
- Severity9.6/10CVSS 9.6
- No patch5/5No fixed version listed; see vendor advisory
What would change the score
- Would score about 87 if added to CISA KEV
- Would score about 82 if CISA's SSVC rates exploitation active
- Would score about 44 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
FortiOS in an affected version range (8.0.0–8.0.1, 7.6.0–7.6.7, 7.4.0–7.4.12, 7.2.0–7.2.13) The attacker must be a configured iBGP neighbor of the device, handled by the BGP daemonWorkaround: No workaround is given in the supplied facts. Since the attacker must be a configured iBGP neighbor, reviewing which iBGP neighbors are configured is a reasonable place to look, but the facts do not specify any mitigation.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-126254 (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…), 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-2026-126254 (entry last updated 2026-11-11):
Affected:
- Fortinet FortiOS: from 8.0.0, through 8.0.1; from 7.6.0, through 7.6.7; from 7.4.0, through 7.4.12; from 7.2.0, through 7.2.13
Fixed versions: none listed yet.
Conditions (all must be true for the bug to be hit):
- FortiOS in an affected version range (8.0.0–8.0.1, 7.6.0–7.6.7, 7.4.0–7.4.12, 7.2.0–7.2.13) (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268)
- The attacker must be a configured iBGP neighbor of the device, handled by the BGP daemon (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-268)
Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on.
Attacker needs: network access, low-privilege login, no user action.
CISA KEV: CVE-2026-126254 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126254 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-26-268
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-2026-126254
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-2026-126254"}.Timeline
- CVE published
- First seen by cve.now
- Posted on X by cve.now
Affected versions
- Fortinet FortiOS
From 8.0.0 · through 8.0.1; From 7.6.0 · through 7.6.7; From 7.4.0 · through 7.4.12; From 7.2.0 · through 7.2.13
Evidence 3
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Link
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-126254
Is CVE-2026-126254 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: cve.now feed data
What does this mean?
A numeric truncation error in FortiOS's BGP handling means a configured iBGP neighbor can send malicious or malformed BGP attributes to all connected routers through a specially crafted request. The impact described is denial of service.Source: fortiguard.fortinet.com
Which versions are affected by CVE-2026-126254?
FortiOS: from 8.0.0 through 8.0.1; from 7.6.0 through 7.6.7; from 7.4.0 through 7.4.12; from 7.2.0 through 7.2.13.Source: cve.now feed data
Am I affected, and how do I check?
FortiOS 8.0.0 through 8.0.1, 7.6.0 through 7.6.7, 7.4.0 through 7.4.12, and 7.2.0 through 7.2.13 are in the listed ranges. The problem involves the BGP daemon and a configured iBGP neighbor, so the FortiOS version and the BGP neighbor configuration are what to check.Source: fortiguard.fortinet.com
How do I fix CVE-2026-126254?
The supplied facts do not name a fixed version or a workaround. Check Fortinet's advisory for the patched release and upgrade to it once confirmed.Source: fortiguard.fortinet.com
What if there's no patch?
No workaround is given in the supplied facts. Since the attacker must be a configured iBGP neighbor, reviewing which iBGP neighbors are configured is a reasonable place to look, but the facts do not specify any mitigation.Source: fortiguard.fortinet.com