Vulnerability · NVD published 2021-04-27
CVE-2021-29441
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.
- First cited attacker
- 1 day →First PoC
Signals
- Exploited in the wild
- Not on KEVNot in CISA's catalogue as of the last daily pull. Absence is not proof of safety.
- EPSS · 30-day forecast
- 83%Chance of exploitation in the next 30 days, 100th percentile of all CVEs. A forecast; KEV outranks it.
- CVSS · NVD · HIGH
- 8.6CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
- Internet exposure
- not stated by sourcesNo exposure census on this CVE's dispatches.
Exploits
1 known · links onlyNuclei1
This template only works on Nuclei engine prior to version 2.3.3 and version >= 2.3.5. 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
yaml · seen 2026-10-18
On the wire
0 dispatchesNo dispatch on our wire has named this CVE yet.
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