CVE-2021-3125Network attack vector

Network service interruption via IPv6 routing loop

Published Apr 12, 2021 · Updated Aug 3, 2024

IPv6 routing in TP-Link TL-XDR routers allows remote attackers to cause a service interrupt via an address within an advertised prefix. The forwarding path sends a packet for a nonlocal address back over a point-to-point link, while the upstream router returns it under the same prefix route. Reachability requires IPv6, an on-link global prefix advertised on the WAN link, and a destination in that prefix that is not assigned locally.

CVSS severity7.5
High
EPSS probability1.50%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

IPv6 routing in TP-Link TL-XDR routers allows remote attackers to cause a service interrupt via an address within an advertised prefix. The forwarding path sends a packet for a nonlocal address back over a point-to-point link, while the upstream router returns it under the same prefix route. Reachability requires IPv6, an on-link global prefix advertised on the WAN link, and a destination in that prefix that is not assigned locally.

The record

CVE
CVE-2021-3125
Published
Apr 12, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-834, T1498
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 12, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.3NISTAV:N/AC:M/Au:N/C:N/I:N/A:P
7.5NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-834Excessive Iteration
T1498Network Denial of Service

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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