CVE-2021-40085Public exploitNetwork attack vector

Authenticated dnsmasq reconfiguration via newline injection

Published Aug 31, 2021 · Updated Aug 4, 2024

Newline injection in OpenStack Neutron before 16.4.1, 17.x before 17.2.1, and 18.x before 18.1.1 allows remote authenticated users to alter dnsmasq. The DHCP option formatter writes unvalidated extra_dhcp_opts values into the dnsmasq options file, so an embedded newline starts attacker-controlled configuration lines. A valid cloud account and permission to update a Neutron port are required; injected options can crash dnsmasq, affect tenants sharing an interface, or trigger code execution when dnsmasq is before 2.81.

CVSS severity7.1
High
EPSS probability1.83%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Newline injection in OpenStack Neutron before 16.4.1, 17.x before 17.2.1, and 18.x before 18.1.1 allows remote authenticated users to alter dnsmasq. The DHCP option formatter writes unvalidated extra_dhcp_opts values into the dnsmasq options file, so an embedded newline starts attacker-controlled configuration lines. A valid cloud account and permission to update a Neutron port are required; injected options can crash dnsmasq, affect tenants sharing an interface, or trigger code execution when dnsmasq is before 2.81.

The record

CVE
CVE-2021-40085
Published
Aug 31, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 31, 2021CVE 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 vectornetwork
Required privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:P/A:N
6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
7.1GitHubCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

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)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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