CVE-2021-24018

Code execution via firmware-verification buffer underwrite

Published Aug 4, 2021 · Updated Oct 25, 2024

Buffer underwrite in Fortinet FortiOS before 7.0.1 allows attackers on an adjacent network to execute code using a crafted firmware image. The firmware verification routine writes before the start of a buffer while processing attacker-supplied image data. Exploitation requires high privileges and access to the firmware upload path; successful memory corruption permits code execution on the appliance.

CVSS severity4.3
Medium
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Buffer underwrite in Fortinet FortiOS before 7.0.1 allows attackers on an adjacent network to execute code using a crafted firmware image. The firmware verification routine writes before the start of a buffer while processing attacker-supplied image data. Exploitation requires high privileges and access to the firmware upload path; successful memory corruption permits code execution on the appliance.

The record

CVE
CVE-2021-24018
Published
Aug 4, 2021
Updated
Oct 25, 2024
Vendor
Fortinet
Product
FortiOS
Classifications
CWE-787
Attack vector
adjacent
Privileges
admin

Timeline

How it unfolded

  1. Aug 4, 2021CVE publishedPublication date reported by the CVE source.
  2. Oct 25, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=FortiOS before 7.0.1

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesadmin

What is affected?

Fortinet · FortiOSversion=FortiOS before 7.0.1

Published CVSS scores

5.8NIST NVDAV:A/AC:L/Au:N/C:P/I:P/A:P
8.8NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
4.3FortinetCVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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