CVE-2021-41436Network attack vector

Unauthenticated service interruption via crafted HTTP packet

Published Nov 19, 2021 · Updated Jul 9, 2026

HTTP request smuggling in affected ASUS router web interfaces allows remote attackers to interrupt service by sending a crafted HTTP packet. The public record attributes the flaw to inconsistent HTTP request interpretation but does not identify the parser or conflicting message-boundary handling. No authentication or user interaction is required; the documented consequence is denial of service, with no published claim of data access or code execution.

CVSS severity7.5
High
EPSS probability4.95%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in affected ASUS router web interfaces allows remote attackers to interrupt service by sending a crafted HTTP packet. The public record attributes the flaw to inconsistent HTTP request interpretation but does not identify the parser or conflicting message-boundary handling. No authentication or user interaction is required; the documented consequence is denial of service, with no published claim of data access or code execution.

The record

CVE
CVE-2021-41436
Published
Nov 19, 2021
Updated
Jul 9, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-444, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Nov 19, 2021CVE publishedPublication date reported by the CVE source.
  2. Jul 9, 2026Record 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.

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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1499.004Application or System Exploitation

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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