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FortiosOperating system · Fortinet

CVE-2025-53843

HIGH · 7.5 CVSS v3.1 Published 2025-11-18
Fix available
A fix is available. Upgrade to 7.4.9 / 7.6.4 or later.
See remediation →
81/100
Remediation priority · High
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
A stack-based buffer overflow vulnerability in Fortinet FortiOS 7.6.0 through 7.6.3, FortiOS 7.4.0 through 7.4.8, FortiOS 7.2 all versions, FortiOS 7.0 all versions, FortiOS 6.4 all versions allows attacker to execute unauthorized code or commands via specially crafted packets

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A stack-based buffer overflow in Fortinet FortiOS allows remote attackers to execute unauthorized code or commands via specially crafted network packets. The vulnerability affects multiple FortiOS version branches (6.4, 7.0, 7.2, 7.4, and 7.6.0-7.6.3) and is exploitable over the network with high attack complexity.

MitigationUpgrade FortiOS to the latest patched version as specified in Fortinet's security advisory. Until patched, restrict network access to FortiOS management interfaces and implement network segmentation to reduce exposure.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
FortiosOperating system
Affected:>= 6.4.0, < 7.4.9>= 7.6.0, < 7.6.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed FortiOS version
    Run 'get system status' in FortiOS CLI or check the web GUI under Dashboard > Status to view the firmware version
    Affected if Version is 6.4.0 through 7.4.8, or 7.6.0 through 7.6.3 (i.e., >= 6.4.0 and < 7.4.9, or >= 7.6.0 and < 7.6.4)
  2. Identify network-exposed management interfaces
    Review interface configuration in FortiOS: go to Network > Interfaces and check which interfaces have Management Access enabled (HTTPS, SSH, HTTP, or Telnet)
    Affected if Management access is enabled on WAN or external-facing interfaces
  3. Audit inbound firewall policies
    Examine firewall policy table via CLI 'get firewall policy' or GUI Policy & Objects > Firewall Policy to identify rules allowing external traffic to management ports
    Affected if Policies permit inbound traffic from untrusted sources to ports 443 (HTTPS), 22 (SSH), or 80 (HTTP) on FortiOS interfaces

System is affected if running a FortiOS version within 6.4.0-7.4.8 or 7.6.0-7.6.3 and the management interface is reachable from the network

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 7.4.9 / 7.6.4 or later
Fixed in 7.4.97.6.4
Interim mitigation

Upgrade FortiOS to the latest patched version as specified in Fortinet's security advisory. Until patched, restrict network access to FortiOS management interfaces and implement network segmentation to reduce exposure.

Recommended fix High confidence

Upgrade to FortiOS 7.4.9 or later (if on 7.0/7.2/7.4/6.4 branches) OR FortiOS 7.6.4 or later (if on 7.6 branch)

  1. 1. Identify the current FortiOS version running on the device using 'get system status' or via FortiManager/FortiCloud
  2. 2. Based on current version, plan upgrade path: if on 6.4.x, upgrade to 7.4.9 or later; if on 7.0.x/7.2.x, upgrade to 7.4.9 or later; if on 7.4.x, upgrade to 7.4.9 or later; if on 7.6.x, upgrade to 7.6.4 or later
  3. 3. Backup current FortiOS configuration using 'execute backup full-config' to local/FTP/SCP
  4. 4. Download the target firmware from Fortinet Customer Support portal (https://support.fortinet.com)
  5. 5. Upload firmware via FortiOS GUI (System > Firmware) or CLI: 'execute system firmware-upgrade <image> [mode]','6. Verify upgrade was successful and system is operational
  6. 7. Confirm the fixed version is running: 'get system status' should show version 7.4.9, 7.6.4, or later
Caveat Review FortiOS release notes for the target version for any configuration or feature changes; major version upgrades (e.g., 6.4 to 7.4) may require configuration adjustments

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fortios Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing10.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,580
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-53843 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data