CVE-2021-25681Public exploitNetwork attack vector

DNS tunneling via arbitrary request-target lookup

Published Apr 20, 2021 · Updated Jul 9, 2026

DNS exfiltration in AdTran Personal Phone Manager 10.8.1 allows remote attackers to tunnel arbitrary data through exposed web servers. The web service accepts an absolute-form GET request and resolves the attacker-controlled DNS name in its request target while the Host header identifies the appliance. Unauthenticated network access to the web service is sufficient to relay arbitrary data or command-and-control traffic through resulting DNS queries.

CVSS severity7.5
High
EPSS probability10.88%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DNS exfiltration in AdTran Personal Phone Manager 10.8.1 allows remote attackers to tunnel arbitrary data through exposed web servers. The web service accepts an absolute-form GET request and resolves the attacker-controlled DNS name in its request target while the Host header identifies the appliance. Unauthenticated network access to the web service is sufficient to relay arbitrary data or command-and-control traffic through resulting DNS queries.

The record

CVE
CVE-2021-25681
Published
Apr 20, 2021
Updated
Jul 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1048.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 20, 2021CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/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.

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)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

T1048.003Exfiltration Over Unencrypted Non-C2 Protocol

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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