How severe is CVE-2021-29441?

CVE-2021-29441 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-29441?

CVE-2021-29441 affects the following packages: com.alibaba.nacos:nacos-common (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-29441?

Update com.alibaba.nacos:nacos-common to 1.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-29441 is resolved across your whole dependency graph.

How do I detect CVE-2021-29441 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for com.alibaba.nacos:nacos-common. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2021-29441 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2021-29441?

O3 pinpoints whether CVE-2021-29441 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2021-29441 actively exploited in the wild?

Yes. There are 5 known exploit references for CVE-2021-29441, including 5 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What type of vulnerability is CVE-2021-29441?

CVE-2021-29441 is classified as CWE-290 (CWE-290). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2021-29441?

A Nuclei detection template exists for CVE-2021-29441, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-29441 published, and has it been updated?

CVE-2021-29441 was published on April 27, 2021 and was last updated on July 9, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

CRITICAL severity

CVE-2021-29441

CRITICALFix: alibaba/nacos#4703

CVE-2021-29441 is a critical-severity (CVSS 9.8) CWE-290 vulnerability in com.alibaba.nacos:nacos-common. 5 public exploit references exist, so weaponization risk is real. O3 Security confirms whether CVE-2021-29441 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Authentication Bypass

Also known asCVE-2021-29442 GHSA-36hp-jr8h-556f GHSA-xv5h-v7jh-p2qh

Published

Apr 27, 2021

Updated

Jul 9, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

5 known

Exploitation data as of Jul 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

☕com.alibaba.nacos:nacos-common

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`com.alibaba.nacos:nacos-common`	all versions	1.4.1

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.