CVE-2021-43105Network attack vector

DNS cache poisoning via out-of-scope NS caching

Published Mar 28, 2022 · Updated Aug 4, 2024

DNS cache poisoning in Technitium DNS Server 7.0 and earlier allows man-in-the-middle attackers to inject arbitrary NS records. The bailiwick check accepts out-of-scope NS records from a forwarder response and stores them in the resolver cache. Exploitation requires a conditional forwarder zone using an attacker-controlled forwarder, or UDP or TCP forwarding exposed to interception; poisoned delegations can redirect later DNS lookups.

CVSS severity4.3
Medium
EPSS probability0.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DNS cache poisoning in Technitium DNS Server 7.0 and earlier allows man-in-the-middle attackers to inject arbitrary NS records. The bailiwick check accepts out-of-scope NS records from a forwarder response and stores them in the resolver cache. Exploitation requires a conditional forwarder zone using an attacker-controlled forwarder, or UDP or TCP forwarding exposed to interception; poisoned delegations can redirect later DNS lookups.

The record

CVE
CVE-2021-43105
Published
Mar 28, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1557
Attack vector
network
Privileges
Unavailable

Timeline

How it unfolded

  1. Mar 28, 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 vectornetwork
Required privilegesUnavailable in this record.

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.0NVDAV:N/AC:L/Au:S/C:N/I:P/A:N
4.3NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A: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
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1557Adversary-in-the-Middle

Public exploit references

No public exploit references are available in this record.

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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