CVE-2021-29441
Medium PUBLISHEDAuthentication bypass
Not yet in CISA KEV
Recommended Action
Treat as actively exploited. Assess exposure, apply compensating controls where patching is delayed, and monitor for abuse.
At a Glance
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.
- Published
- Apr 27, 2021
- First Seen
- Jun 28, 2025
- CVSS
- 8.6 High
- EPSS
- —
Recommended Actions
- Treat as actively exploited. Assess exposure, apply compensating controls where patching is delayed, and monitor for abuse.
- Check enrichment artifacts for scanner coverage and available PoCs before rolling remediation validation.
- Use the Pro API to automate enrichment, telemetry, and workflow delivery for VM, SOC, and CTI pipelines.
Known Exploited Vulnerability Sources
Catalogues that list this CVE as a known exploited vulnerability.
| Source | Added |
|---|---|
| The Shadowserver (via CIRCL) First | 2025-06-28 00:00 UTC |
Detection Context
Request patterns and scanner artifacts observed for this CVE. Operational detection logic guidance is coming soon.
Scanner Artifacts
Nuclei and Metasploit references linked to this CVE.
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-29441.yaml | Apr 25, 2025 |
CVSS Scores
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Exploitation Status
Exploited in the wild
Recorded 2026-05-30 00:00:00 UTC · The Shadowserver (via CIRCL)
Proof of concept available
Recorded 2022-03-15 08:53:59 UTC · GitHub
Weaknesses (CWE)
-
Authentication Bypass by Spoofing
Scanner Integrations
| Scanner | Reference | Detected |
|---|---|---|
| Nuclei | https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-29441.yaml | Apr 25, 2025 |
Potential Proof of Concepts
These PoCs are unverified and could contain malware. Use at your own risk.
github · Created 2022-03-15 08:53:59 UTC · 2 stars
nuclei · Created Unknown
Timeline
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Added to KEVIntel
-
Detected by Nuclei
-
Proof of Concept Exploit Available
-
CVE Published to Public
-
CVE ID Reserved
Automate This Intelligence with the Pro API
Confidence scoring, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.
Pro API Example
GET /api/v2/pro/kevs/CVE-2021-29441
{
"cve_id": "CVE-2021-29441",
"title": "Authentication bypass",
"affected_vendor": "alibaba",
"affected_product": "nacos",
"confidence": "Medium",
"cvss_score": 8.6,
"epss_score": null,
"exploit_status": {
"exploited_in_the_wild": true,
"active_exploitation_observed": false
},
"sensor_telemetry": { "...": "Pro API fields" },
"proof_of_concepts": [ "..." ],
"scanner_integrations": [ "..." ]
}