CVE-2021-29441
Authentication bypass
- Published
- Apr 27, 2021
- Updated
- Aug 3, 2024
- Assigning CNA
- GitHub_M
- Evidence observed
- Aug 8, 2026
Primary CVSS
nvd · CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HHigh · next 30 days
- Percentile
- 99.7%
- Model date
- Oct 15, 2026
EPSS is a statistical estimate, not a certainty or a measure of impact. Combine it with CVSS, KEV status, exposure and your environment.
Summary
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.
Sources
- Vulhub vulnerability labs
Declared conditions
- lab image version: vulhub/nacos:1.4.0(nacos/CVE-2021-29441/docker-compose.yml:services.web.image)
http/cves/2021/CVE-2021-29441.yaml
Nuclei TemplatesDeclared conditions
- network: http($.protocol_keys)
- verification: dsl,word($.matchers[*].type)
Responsible use
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