CVE-2021-29441
This filter has a backdoor that enables Nacos servers to bypass this filter and therefore skip authentication checks.
Does this matter?
EPSS puts the probability of exploitation in the next 30 days at 83.2%, higher than 100% of all known CVEs. Patch or mitigate before the next change window.
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.
- CVSS 3.1
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 83.25% probability · 100th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-290
- Affected
- alibaba/nacos
- Source
- security-advisories@github.com
EPSS moved from 83.5% on 24 September 2026 to 83.2% on 26 October 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
References
- https://github.com/advisories/GHSA-36hp-jr8h-556fExploit, Third Party Advisory
- https://github.com/alibaba/nacos/issues/4701Exploit, Third Party Advisory
- https://github.com/alibaba/nacos/pull/4703Patch, Third Party Advisory
- https://github.com/advisories/GHSA-36hp-jr8h-556fExploit, Third Party Advisory
- https://github.com/alibaba/nacos/issues/4701Exploit, Third Party Advisory
- https://github.com/alibaba/nacos/pull/4703Patch, Third Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.