CVE-2021-40423Public exploitNetwork attack vector

API outage via stalled command requests

Published Jan 28, 2022 · Updated Apr 15, 2025

Denial of service in Reolink RLC-410W 3.0.0.136_20121102 allows remote attackers to interrupt its CGI API with crafted HTTP requests. In cgiserver.cgi, non-string command entries never complete and occupy incoming-request slots until their 16-second timeout expires. Repeated unauthenticated requests fill the 20-request queue, leaving the CGI endpoint unreachable for close to a minute.

CVSS severity7.5
High
EPSS probability1.34%
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 Reolink RLC-410W 3.0.0.136_20121102 allows remote attackers to interrupt its CGI API with crafted HTTP requests. In cgiserver.cgi, non-string command entries never complete and occupy incoming-request slots until their 16-second timeout expires. Repeated unauthenticated requests fill the 20-request queue, leaving the CGI endpoint unreachable for close to a minute.

The record

CVE
CVE-2021-40423
Published
Jan 28, 2022
Updated
Apr 15, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-20, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 28, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 2025Record 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

7.5Cisco TalosCVSS:3.0/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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation
T1499.003Application Exhaustion Flood

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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