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CVE-2021-29441:
Authentication Bypass

9.8

CVSS Score
3.1

Basic Information

EPSS Score
0.99887%
Published
4/27/2021
Updated
2/1/2023
KEV Status
No
Technology
TechnologyJava

Technical Details

CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Package NameEcosystemVulnerable VersionsFirst Patched Version
com.alibaba.nacos:nacos-commonmaven< 1.4.11.4.1

Vulnerability Intelligence
Miggo AIMiggo AI

Miggo AIRoot Cause Analysis

The vulnerability stems from AuthFilter's handling of the User-Agent header in its doFilter method. When authConfigs.isEnableUserAgentAuthWhite() is true (default), any request with 'Nacos-Server' User-Agent bypasses authentication. This is explicitly shown in the code snippet from the GitHub issue where the filter skips security checks for these requests. The function appears in the call stack when processing malicious requests with spoofed headers, making it the primary runtime indicator.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

WAF Protection Rules

WAF Rule

W**n *on*i*ur** to us* *ut**nti**tion (`-*n**os.*or*.*ut*.*n**l**=tru*`) N**os us*s t** `*ut**ilt*r` s*rvl*t *ilt*r to *n*or** *ut**nti**tion. T*is *ilt*r **s * [***k*oor](*ttps://*it*u*.*om/*li****/n**os/*lo*/****************************************

Reasoning

T** vuln*r**ility st*ms *rom `*ut**ilt*r`'s **n*lin* o* t** `Us*r-***nt` *****r in its `*o*ilt*r` m*t*o*. W**n `*ut**on*i*s.is*n**l*Us*r***nt*ut*W*it*()` is tru* (****ult), *ny r*qu*st wit* 'N**os-S*rv*r' `Us*r-***nt` *yp*ss*s *ut**nti**tion. T*is is