CVE-2021-42755

Adjacent unauthenticated DHCP service crash via integer wraparound

Published Jul 18, 2022 · Updated Aug 4, 2024

Integer overflow in FortiSwitch and related Fortinet products allows adjacent remote attackers to crash the dhcpd daemon. Fortinet identifies integer wraparound in dhcpd but has not published the affected calculation or the DHCP input that triggers it. The attack requires no authentication but does require adjacent-network access, and its reported consequence is interruption of DHCP service rather than device takeover.

CVSS severity4.3
Medium
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in FortiSwitch and related Fortinet products allows adjacent remote attackers to crash the dhcpd daemon. Fortinet identifies integer wraparound in dhcpd but has not published the affected calculation or the DHCP input that triggers it. The attack requires no authentication but does require adjacent-network access, and its reported consequence is interruption of DHCP service rather than device takeover.

The record

CVE
CVE-2021-42755
Published
Jul 18, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-190, T1499.004
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 18, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3Fortinet, Inc.CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
4.3NIST NVDCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound
T1499.004Application or System Exploitation

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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