CVE
A stack-based buffer overflow vulnerability in Fortinet FortiAuthenticator 8.0.0 through 8.0.3, FortiAuthenticator 6.6.0 through 6.6.10…
- Exploited
- No known exploitation
- Fix
- Fixed in 8.0.4 or above
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 8.0.4 or above.
- 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? →
- 39/100 · 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
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
Who should check
Teams running FortiAuthenticator 8.0.0 through 8.0.3 or 6.6.0 through 6.6.10
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed, reachable over the network without a login · Unknown: Advisories don't say whether default setups are affected
- Reach14/20Affects Fortinet (an enterprise product or network appliance)
- Severity7.5/10CVSS 7.5
- No patch0/5No signal
What would change the score
- Would score about 84 if added to CISA KEV
- Would score about 79 if CISA's SSVC rates exploitation active
- Would score about 44 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 8.0.4 or above.
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-2026-126239 (A stack-based buffer overflow vulnerability in Fortinet FortiAuthenticator 8.0.0 through 8.0.3, FortiAuthenticator 6.6.0 through 6.6.10…), 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-2026-126239 (entry last updated 2026-11-11):
Affected:
- Fortinet FortiAuthenticator: from 8.0.0, through 8.0.3; from 6.6.0, through 6.6.10
Fixed versions: 8.0.4 or above.
Conditions (all must be true for the bug to be hit):
- Runs FortiAuthenticator 8.0.0 through 8.0.3 (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-254)
- Runs FortiAuthenticator 6.6.0 through 6.6.10 (source: https://fortiguard.fortinet.com/psirt/FG-IR-26-254)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, no user action.
CISA KEV: CVE-2026-126239 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-126239 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-26-254
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-2026-126239
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-2026-126239"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- Fortinet FortiAuthenticator
From 8.0.0 · through 8.0.3; From 6.6.0 · through 6.6.10
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-2026-126239
Is CVE-2026-126239 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 stack-based buffer overflow lets data written past a fixed-size buffer on the stack overwrite nearby memory. The facts say an attacker can use this to execute unauthorized code or commands.Source: fortiguard.fortinet.com
Which versions are affected by CVE-2026-126239?
FortiAuthenticator: from 8.0.0 through 8.0.3; from 6.6.0 through 6.6.10.Source: cve.now feed data
Am I affected, and how do I check?
FortiAuthenticator 8.0.0 through 8.0.3 and 6.6.0 through 6.6.10 are listed as affected. To check a deployment, compare the running FortiAuthenticator version against those ranges.Source: fortiguard.fortinet.com
How do I fix CVE-2026-126239?
Upgrade to FortiAuthenticator 8.0.4 or above, per the vendor advisory quote. The facts list no workaround.Source: fortiguard.fortinet.com