CVE
A authentication bypass by primary weakness vulnerability in Fortinet FortiOS 8.0.0 through 8.0.1, FortiOS 7.6.0 through 7.6.7, FortiOS…
Affects FortiOS 8.0.0-8.0.1, 7.6.0-7.6.7, 7.4.0-7.4.12, 7.2.0-7.2.13 and 7.0.1-7.0.19 with the OSPF daemon. Fixed in 8.0.2, 7.6.8, 7.4.13 and 7.2.14.
Written by anthropic/claude-sonnet-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 8.0.2, 7.6.8, 7.4.13, 7.2.14
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 8.0.2, 7.6.8, 7.4.13, 7.2.14.
- 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? →
- 23/100 · 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? →
- Unclear
- 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 an authentication bypass flaw that lets an attacker broadcast OSPF-style link-state advertisements (LSAs) using a specially crafted request, without logging in. The attacker must be on the same local network segment as the device, and no user interaction is needed. Wait, the facts only say "LSA," so I should not expand it. Corrected: Fortinet FortiOS has an authentication bypass flaw that lets an unauthenticated attacker broadcast LSAs by sending a specially crafted request. The attacker needs to be on the same local network as the device, but does not need to log in.
Read the original description
A authentication bypass by primary weakness 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 an unauthenticated attacker to broadcast LSA via specially crafted request
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure?/25Unknown. Advisories don't say whether default setups are affected
- Reach14/20Affects Fortinet (an enterprise product or network appliance)
- Severity9.3/10CVSS 9.3
- No patch0/5No signal
What would change the score
- Would score about 78 if added to CISA KEV
- Would score about 73 if CISA's SSVC rates exploitation active
- Would score about 45 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 8.0.2, 7.6.8, 7.4.13, 7.2.14.
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-2026-126253 (A authentication bypass by primary weakness vulnerability in Fortinet FortiOS 8.0.0 through 8.0.1, FortiOS 7.6.0 through 7.6.7, FortiOS…), 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-2026-126253 (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; from 7.0.1, through 7.0.19
Fixed versions: 8.0.2, 7.6.8, 7.4.13, 7.2.14.
Conditions (all must be true for the bug to be hit):
- FortiOS in an affected version (8.0.0-8.0.1, 7.6.0-7.6.7, 7.4.0-7.4.12, 7.2.0-7.2.13, or 7.0.1-7.0.19) with the OSPF daemon (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-267)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: adjacent access, no login, no user action.
CISA KEV: CVE-2026-126253 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126253 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-26-267
- https://www.cve.org/CVERecord?id=CVE-2026-126253
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-2026-126253
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-2026-126253"}.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; From 7.0.1 · through 7.0.19
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-2026-126253
Is CVE-2026-126253 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?
The OSPF daemon in FortiOS has an authentication bypass. An unauthenticated attacker could broadcast OSPF link-state advertisements (LSAs) with a specially crafted request.Source: fortiguard.fortinet.com, cve.org
Which versions are affected by CVE-2026-126253?
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; from 7.0.1 through 7.0.19.Source: cve.now feed data
Am I affected, and how do I check?
FortiOS 8.0.0-8.0.1, 7.6.0-7.6.7, 7.4.0-7.4.12, 7.2.0-7.2.13 and 7.0.1-7.0.19 with the OSPF daemon are listed. Check the installed FortiOS version and whether OSPF is configured on the device.Source: fortiguard.fortinet.com, cve.org
How do I fix CVE-2026-126253?
Upgrade to FortiOS 8.0.2, 7.6.8, 7.4.13 or 7.2.14 or later, matching the installed branch. The advisory lists no workaround, and no fixed version is named for the 7.0 branch.Source: fortiguard.fortinet.com, cve.org