`CVE-2021-29441` Nacos

Affected software	Nacos
Severity	9.8 Critical CVSS 3.1 3 scores
Fixed in	`1.4.1`
Weakness	Missing authentication (CWE-306)
Published	27 Apr 2021
Updated	17 Jun 2026

Description

Nacos is a platform designed for dynamic service discovery and configuration and service management. In Nacos before version 1.4.1, when configured to use authentication (-Dnacos.core.auth.enabled=true) Nacos uses the AuthFilter servlet filter to enforce authentication. This filter has a backdoor that enables Nacos servers to bypass this filter and therefore skip authentication checks. This mechanism relies on the user-agent HTTP header so it can be easily spoofed. This issue may allow any user to carry out any administrative tasks on the Nacos server.

CWE-290

Exploitation status

Exploited

Real-world exploitation reported by VulnCheck KEV. CISA has not confirmed it.

CISA KEV not listed
VulnCheck KEV listed Exploitation reported in the wild. 8 citations · honeypot sightings · 4 exploits · earliest 2023-12-01.
CISA Vulnrichment no assessment published
Indexed PoC 3 indexed Published artifacts you can open, in GitHub PoC, Nuclei; first seen 2022-03-15.
EPSS 83% chance in 30 days A model's forecast, not a report of exploitation. Higher than 99.7% of all scored CVEs.

VulnCheck KEV

Exploitation evidence from VulnCheck Known Exploited Vulnerabilities (VulnCheck KEV), used under VulnCheck's community terms. View CVE-2021-29441 in VulnCheck (free account), which lists 3 more citations not shown here.

Evidence	Source	Detail	Date
Honeypot sighting	Shadowserver honeypots	Exploitation attempts seen on 609 days	2023-12-01 to 2026-11-12
Reported exploitation	info.greynoise.io	/hubfs/resources/GreyNoise-2025-Mass-Internet-Exploitation-Report.pdf	2025-02-27
Reported exploitation	webflow.sysdig.com	/blog/jadepuffer-agentic-ransomware-for-automated-database-extortion	2026-07-01
Reported exploitation	socradar.io	/blog/wp-shellstorm-expose-1-4m-wordpress-sites	2026-07-09
Reported exploitation	techgines.com	/post/wp-shellstorm-webshell-brokerage-wordpress-joomla-exposed	2026-07-11
Reported exploitation	recordedfuture.com	/blog/july-2026-cve-landscape	2026-08-07
Exploit reference	VulnCheck XDB e32b9a63dcf6	Exploit type: remote-with-credentials	2022-03-15
Exploit reference	VulnCheck XDB d37303dbb22a	Exploit type: initial-access	2023-10-12
Exploit reference	VulnCheck XDB a7f1b2841050	Exploit type: initial-access	2026-06-26
Exploit reference	VulnCheck XDB 5f8373decc24	Exploit type: initial-access	2026-10-08

Evidence

Source

Detail

Date

Honeypot sighting

Shadowserver honeypots

Exploitation attempts seen on 609 days

2023-12-01 to 2026-11-12

Reported exploitation

info.greynoise.io

/hubfs/resources/GreyNoise-2025-Mass-Internet-Exploitation-Report.pdf

2025-02-27

Reported exploitation

webflow.sysdig.com

/blog/jadepuffer-agentic-ransomware-for-automated-database-extortion

2026-07-01

Reported exploitation

socradar.io

/blog/wp-shellstorm-expose-1-4m-wordpress-sites

2026-07-09

Reported exploitation

techgines.com

/post/wp-shellstorm-webshell-brokerage-wordpress-joomla-exposed

2026-07-11

Reported exploitation

recordedfuture.com

/blog/july-2026-cve-landscape

2026-08-07

Exploit reference

VulnCheck XDB e32b9a63dcf6

Exploit type: remote-with-credentials

2022-03-15

Exploit reference

VulnCheck XDB d37303dbb22a

Exploit type: initial-access

2023-10-12

Exploit reference

VulnCheck XDB a7f1b2841050

Exploit type: initial-access

2026-06-26

Exploit reference

VulnCheck XDB 5f8373decc24

Exploit type: initial-access

2026-10-08

2 of these are GitHub repositories with fewer than 5 stars. They are listed for reference and don't count toward the exploitation status above.

Index	Artifact	Stars	First seen
GitHub PoC	bysinks/CVE-2021-29441	2	2022-03-15
GitHub PoC	Vulhub nacos/CVE-2021-29441: Nacos User-Agent Authentication Bypass (CVE-2021-29441), run with Isoloom		2026-10-08
Nuclei	Nacos <1.4.1 - Authentication Bypass

Index

Artifact

Stars

First seen

GitHub PoC

bysinks/CVE-2021-29441

2022-03-15

GitHub PoC

Vulhub nacos/CVE-2021-29441: Nacos User-Agent Authentication Bypass (CVE-2021-29441), run with Isoloom

2026-10-08

Nuclei

Nacos <1.4.1 - Authentication Bypass

Waratek protection

Outside Waratek scope

A Java vulnerability, but not one Waratek protects. It affects only Java on a user's desktop (applets, Web Start, JavaFX, the installer), sits in a product the Waratek agent can't be installed into, or is in a package we don't expect in business applications. The decision below says which.

Protection none
Action not pursued none
Review automated Upstream data
Record active

Decided by	An OSV.dev record of this CVE affecting a package published to Maven Central. When every such package is one business applications do not use (Minecraft mods and launchers, Fastjson) and no tracked product is named by CPE, it settles the CVE as Outside Waratek scope instead
Finding	Every Maven package this CVE affects (com.alibaba.nacos:nacos-common) is on the excluded_maven_packages list in known-products.yaml, so it is not reviewed.

Decided by

An OSV.dev record of this CVE affecting a package published to Maven Central. When every such package is one business applications do not use (Minecraft mods and launchers, Fastjson) and no tracked product is named by CPE, it settles the CVE as Outside Waratek scope instead

Finding

Every Maven package this CVE affects (com.alibaba.nacos:nacos-common) is on the excluded_maven_packages list in known-products.yaml, so it is not reviewed.

CVSS

9.8 CRITICAL v3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H 3 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

Version Score Band Vector Assigner Type

CVSS 3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H NVD Primary published

CVSS 3.1 8.6 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N security-advisories@github.com Secondary

CVSS 2.0 7.5 none AV:N/AC:L/Au:N/C:P/I:P/A:P NVD Primary

Version	Score	Band	Vector	Assigner	Type
CVSS 3.1	9.8	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`	NVD	Primary	published
CVSS 3.1	8.6	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N`	security-advisories@github.com	Secondary
CVSS 2.0	7.5	none	`AV:N/AC:L/Au:N/C:P/I:P/A:P`	NVD	Primary

Affected software and releases

Maven packages

Affected and fixed versions, from OSV.dev

Package Introduced Fixed Last affected

com.alibaba.nacos:nacos-common 0 1.4.1 unbounded

Package	Introduced	Fixed	Last affected
`com.alibaba.nacos:nacos-common`	0	`1.4.1`	unbounded

Products and versions

2 products, 2 version entries

Source	Vendor	Product	Scheme	Affected versions
nvd	alibaba	nacos	generic	＜ 1.4.1
osv	com.alibaba.nacos	nacos-common	generic	＜ 1.4.1

Source

Vendor

Product

Scheme

Affected versions

nvd

alibaba

nacos

generic

＜ 1.4.1

osv

com.alibaba.nacos

nacos-common

generic

＜ 1.4.1

References

URL	Tags
https://github.com/alibaba/nacos/issues/4701	WEB
https://github.com/alibaba/nacos/pull/4703	WEB
https://github.com/advisories/GHSA-36hp-jr8h-556f	ADVISORY
https://github.com/alibaba/nacos/issues/4463	WEB
https://github.com/alibaba/nacos/pull/4517	WEB

URL

Timeline

Published	2021-04-27	By the CVE Program.
VulnCheck KEV: earliest evidence	2023-12-01	Date of the oldest evidence of exploitation in VulnCheck KEV's record. VulnCheck does not publish the date it listed the CVE.
NVD record modified	2026-06-17	NVD's own last-modified date for this record.
VulnCheck KEV: latest evidence	2026-11-12	Date of the newest report, exploit reference or honeypot sighting in VulnCheck KEV's record.

Published

2021-04-27

By the CVE Program.

VulnCheck KEV: earliest evidence

2023-12-01

Date of the oldest evidence of exploitation in VulnCheck KEV's record. VulnCheck does not publish the date it listed the CVE.

NVD record modified

2026-06-17

NVD's own last-modified date for this record.

VulnCheck KEV: latest evidence

2026-11-12

Date of the newest report, exploit reference or honeypot sighting in VulnCheck KEV's record.

How VRT decided (9 of 24 rules ran)

9 of 24 rules ran. The rest didn't run because an earlier rule had already settled the CVE.

# Rule Outcome Status Detail

identity: Does this identifier describe a vulnerability at all? the first rule that matches decides

1 rejected no match CVE Program withdrawal of this identifier

scope: Is it a vulnerability Waratek protects? the first rule that matches decides

2 armr-patch-file no match An ARMR patch file on disk for this CVE

3 armr-secure-rule-file no match An ARMR security-rule template on disk for this CVE

4 manual-classification no match A researcher's recorded decision for this specific CVE

5 manual classification no match Manual classification of this CVE in the legacy dataset

6 non-java-upstream no match A root cause in non-Java code: an OS kernel, a C library, or a bundled runtime

7 oracle-component no match The defect being in a component of a tracked product the agent does not reach: JavaFX, the Java SE installer, the JInitiator browser plug-in, the native WebLogic proxy plug-in, or a native part of Oracle Application Server or Collaboration Suite (HTTP Server, Web Cache, Internet Directory, mail and calendar servers). Oracle gives these no CPE of their own and names them only in the description.

8 java-client-side no match Oracle's own risk-matrix note saying the CVE is reached only through untrusted code in the Java sandbox (applets, Web Start) or only through a client installation of Java, so a server running its own trusted code is not exposed

9 osv-maven decided it matched Outside Waratek scope Maven packages excluded by policy: com.alibaba.nacos:nacos-common

10 cna-maven-package not reached An affected Maven artifact named by the CNA itself

11 known-cpe-product not reached An NVD CPE naming a product ARMR tracks

12 cna-cpe-product not reached A CPE the CNA published naming a tracked product. Oracle publishes these on advisory day, months before NVD.

13 oracle-advisory-family not reached A tracked product family named in Oracle's own risk matrix. CPE cannot carry a suite name, only a module.

14 cna-named-product not reached A tracked product named in words by the CVE's own CNA, on a record with no CPE yet. Apache and Eclipse publish these on advisory day, before NVD adds CPE data.

15 non-deployable-product not reached The only affected product being a sealed appliance image, where Java runs but no -javaagent can be attached

16 unmatched-product not reached No tracked product matched above, and none present at all

disposition: What do we do about one that is? every rule runs

17 patch-hint not reached A reference pointing at the upstream fix: a commit, a PR, a Red Hat bug

18 open-source-maven not reached The affected package being open source on Maven, so the fix can be read

19 poc-derivable not reached An indexed exploit clearing the evidence bar to reverse-engineer, where there is no source to read

20 no-exploit not reached Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read

21 secure-rule-match not reached A vulnerability class already blocked by an ARMR security rule

22 exploited-no-fix-or-poc not reached Somebody exploiting this CVE (a CISA or VulnCheck KEV listing, or a CISA verdict of active exploitation), with no fix, source code or PoC to build a rule from

23 below-action-threshold not reached Medium or Low severity, no CISA or VulnCheck KEV listing, no PoC clearing the evidence bar, no CISA verdict, no Oracle advisory

24 no-exploit-published not reached Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all

Products the scope rules checked

The products this CVE's record names, and whether VRT tracks each one. The scope rules decided on these.

Vendor Product Tracked CPE Source

alibaba nacos not tracked cpe:2.3:a:alibaba:nacos:*:*:*:*:*:*:*:*

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