What it is
CVE-2021-29441 is an unauthenticated Authentication bypass affecting alibaba nacos. Nacos is a platform designed for dynamic service discovery and configuration and service management. In Nacos before version 1.4.1,...
Vulnerability report
Exploited in the wild
High confidence
Not in CISA KEV
CVE-2021-29441
Authentication bypass
Alibaba / nacos · affected before 1.4.1
- Severity
- CVSS 8.6 · High
- Confidence
- High
- Exploit status
- Exploited in the wild
- EPSS
- 69.6%
- First observed
- —
- Last observed
- —
Decision summary
What security teams need to know first
Direct answers before the deeper technical record.
Is it exploited?
Yes. KEV Intelligence tracks this CVE as a known exploited vulnerability. Confidence is high.
Who is affected?
alibaba / nacos affected before 1.4.1.
What should we do?
Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.
Overview
Nacos is a platform designed for dynamic service discovery and configuration and service management
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.
Vendor
Product
Affected
Status
alibaba
nacos
Before 1.4.1
Affected
- Published
- 27 Apr 2021
- Exploitation Reported
- 30 May 2026
- Attack vector
- Remote
- Complexity
- Low
- Privileges
- None
- User interaction
- None
Tags
nuclei_scanner
CVE References
- CVE Record CVE.org · CVE Record https://www.cve.org/CVERecord?id=CVE-2021-29441
- GitHub — alibaba/nacos github.com · CVE Record https://github.com/alibaba/nacos/issues/4701
- GitHub — advisories/GHSA-36hp-jr8h-556f github.com · CVE Record https://github.com/advisories/GHSA-36hp-jr8h-556f
- GitHub — alibaba/nacos github.com · CVE Record https://github.com/alibaba/nacos/pull/4703
Exploitation evidence
Why KEV Intelligence marks this CVE as exploited
Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.
Exploited in the wild
The Shadowserver
Independent exploitation attestation added to the KEV Intelligence record.
Proof of concept available
GitHub
Public scanner or PoC coverage increases practical exploitability.
Known exploited vulnerability sources
Per-source evidence links for KEV attestations are available through the KEV Intelligence Pro API.
Learn about Pro API access| Source | Added |
|---|---|
| The Shadowserver First | 2025-06-28 00:00 UTC |
Detection
Operational artifacts and observed signals
Make the evidence actionable in scanner, SOC, and edge-control workflows.
Observed signals
- Request targets
- 0
- User-Agents
- 0
Raw values available in Pro and Enterprise.
Scanner coverage
Nuclei template detected 25 Apr 2025.
View Nuclei template (opens in new tab)Virtual patch status
No KEV Intelligence virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.
Learn about virtual patches →Scanner Artifacts
Scanner and exploit-framework references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-29441.yaml | 25 Apr 2025 |
Risk and context
Severity, weaknesses, and research context
CVSS v3.1
8.6
High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
EPSS
69.6%
Weaknesses
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
Nacos <1.4.1 - Authentication Bypass
nuclei · Created Unknown
Timeline
From disclosure to observed exploitation
-
Public PoC available
Public proof-of-concept code published
-
Added to KEV Intelligence KEV Feed
High-confidence, third-party attested exploitation
-
Nuclei template available
Scanner coverage available
-
CVE published
Vulnerability disclosed publicly
-
CVE ID reserved
Identifier reserved by the CNA
Pro API
Automate this intelligence
Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
- Evidence confidence and provenance
- First-party sensor telemetry
- PoC and scanner references
- Affected versions and enrichment
- Automation-ready JSON delivery
GET /api/v2/pro/kevs/CVE-2021-29441
Free JSON includes basic KEV fields{
"cve_id": "CVE-2021-29441",
"confidence": "High",
"cvss_score": 8.6,
"cvss_estimated": false,
"epss_score": 0.69634,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "attempts": 0, "sensors": 0 }
}Early warning alerts
Get alerts on high-impact exploitation
Receive curator-selected alerts when exploitation activity warrants attention. Each alert includes the evidence and context needed to decide what requires attention now.