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Fencer Vulns
high 8.6

CVE-2021-29441 in the critical feed json

Authentication bypass

published 2021-04-27 5 y ago modified 2026-07-08 4 mo ago also CVE-2021-29442 , GHSA-36hp-jr8h-556f , GHSA-xv5h-v7jh-p2qh , EUVD-2021-0744

cvss
8.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
83.2%
EPSS 83.2% chance of exploitation in 30 days, percentile 99.6%
public exploits
0
none known, plus a Nuclei check

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.

Patch / fix

  • maven com.alibaba.nacos:nacos-common 1.4.1
  • alibaba nacos 1.4.1

Exploit prediction

83.24% chance of exploitation in the next 30 days, higher than 99.6% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Nuclei template Nacos <1.4.1 - Authentication Bypass nuclei detection template
  • github.com https://github.com/alibaba/nacos/issues/4701 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/advisories/GHSA-36hp-jr8h-556f referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 7.5 AV:N/AC:L/Au:N/C:P/I:P/A:P

Affected packages

ecosystem package affected fixed in
maven com.alibaba.nacos:nacos-common
<1.4.1
1.4.1

Affected products

  • alibaba nacos

Classification

Weakness
  • CWE-290 Authentication Bypass by Spoofing
  • CWE-306 Missing Authentication for Critical Functionality

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.