CVE-2021-45741Network attack vector

Unauthenticated router crash via relay6to4 stack overflow

Published Feb 4, 2022 · Updated Aug 4, 2024

Stack-based buffer overflow in TOTOLINK X5000R firmware 9.1.0u.6118_B20201102 allows remote attackers to crash the router via relay6to4. The setIpv6Cfg function processes an oversized relay6to4 value without enforcing the destination stack buffer's bounds, overwriting adjacent stack memory. No authentication or user interaction is required, and the documented consequence is a network-triggered service interruption rather than data access or modification.

CVSS severity7.5
High
EPSS probability1.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in TOTOLINK X5000R firmware 9.1.0u.6118_B20201102 allows remote attackers to crash the router via relay6to4. The setIpv6Cfg function processes an oversized relay6to4 value without enforcing the destination stack buffer's bounds, overwriting adjacent stack memory. No authentication or user interaction is required, and the documented consequence is a network-triggered service interruption rather than data access or modification.

The record

CVE
CVE-2021-45741
Published
Feb 4, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 4, 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 privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.8NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:C

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499Endpoint 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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