CVE-2021-40406Network attack vector

Unauthenticated login denial via session exhaustion

Published Jan 28, 2022 · Updated Apr 15, 2025

Denial of service in Reolink RLC-410W v3.0.0.136_20121102 allows remote attackers to block camera logins via crafted HTTP requests. The cgiserver.cgi session-creation path accepts a Login command with an empty JSON body, creates a session whose status is neither valid nor invalid, and never removes it; repeated requests exhaust the in-memory session list. The attack requires no authentication or user interaction and interrupts login availability without disclosed confidentiality or integrity impact.

CVSS severity7.5
High
EPSS probability1.53%
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 v3.0.0.136_20121102 allows remote attackers to block camera logins via crafted HTTP requests. The cgiserver.cgi session-creation path accepts a Login command with an empty JSON body, creates a session whose status is neither valid nor invalid, and never removes it; repeated requests exhaust the in-memory session list. The attack requires no authentication or user interaction and interrupts login availability without disclosed confidentiality or integrity impact.

The record

CVE
CVE-2021-40406
Published
Jan 28, 2022
Updated
Apr 15, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, T1499.002
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 exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.002Service Exhaustion

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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