CVE-2021-29441Public exploitNetwork attack vector

Unauthenticated administration via spoofed User-Agent trust

Published Apr 27, 2021 · Updated Aug 3, 2024

Authentication bypass in Alibaba Group Nacos before 1.4.1 allows remote attackers to perform administrative actions through HTTP requests. AuthFilter treats the attacker-controlled User-Agent value Nacos-Server as proof that a request came from a trusted Nacos server and skips credential validation. The flaw is reachable only when authentication is enabled, and successful requests can access protected console or REST API functions without credentials.

CVSS severity9.8
Critical
EPSS probability87.75%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in Alibaba Group Nacos before 1.4.1 allows remote attackers to perform administrative actions through HTTP requests. AuthFilter treats the attacker-controlled User-Agent value Nacos-Server as proof that a request came from a trusted Nacos server and skips credential validation. The flaw is reachable only when authentication is enabled, and successful requests can access protected console or REST API functions without credentials.

The record

CVE
CVE-2021-29441
Published
Apr 27, 2021
Updated
Aug 3, 2024
Vendor
Alibaba Group
Product
Nacos
Classifications
CWE-290, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 27, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.4.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Alibaba Group · Nacosversion=< 1.4.1

Published CVSS scores

7.5National Vulnerability DatabaseAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.6GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

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-290Authentication Bypass by Spoofing
T1190Exploit Public-Facing Application

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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