CVE-2021-23270Network attack vector

Denial of service via IPv6 routing loop

Published Apr 12, 2021 · Updated Aug 3, 2024

Denial of service in Gargoyle OS 1.12.0 allows remote attackers to overload a router and its upstream link with looping IPv6 traffic. The odhcp6c ra_process path installs an on-link prefix route from a router advertisement even when the interface is point-to-point, and netifd lacks a compensating unreachable route for the off-link address. IPv6 must be enabled, the advertisement must mark a global prefix on-link, and traffic must target a nonlocal address in that prefix; the affected router and upstream router then return the packet to each other and consume network capacity.

CVSS severity7.5
High
EPSS probability1.03%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Gargoyle OS 1.12.0 allows remote attackers to overload a router and its upstream link with looping IPv6 traffic. The odhcp6c ra_process path installs an on-link prefix route from a router advertisement even when the interface is point-to-point, and netifd lacks a compensating unreachable route for the off-link address. IPv6 must be enabled, the advertisement must mark a global prefix on-link, and traffic must target a nonlocal address in that prefix; the affected router and upstream router then return the packet to each other and consume network capacity.

The record

CVE
CVE-2021-23270
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

4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS: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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