How severe is CVE-2021-21403?

CVE-2021-21403 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-21403?

CVE-2021-21403 affects the following packages: github.com/kongchuanhujiao/server (Go). Ecosystems affected: Go.

How do I fix CVE-2021-21403?

Update github.com/kongchuanhujiao/server to 1.3.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21403 is resolved across your whole dependency graph.

How do I detect CVE-2021-21403 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/kongchuanhujiao/server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-21403 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2021-21403 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-21403 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-21403?

CVE-2021-21403 has an EPSS (Exploit Prediction Scoring System) score of 1.4%, placing it in the 71th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-21403?

CVE-2021-21403 is classified as CWE-305 (CWE-305), Improper Authentication (CWE-287). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-21403 published, and has it been updated?

CVE-2021-21403 was published on March 26, 2021 and was last updated on July 8, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

CRITICAL severity

CVE-2021-21403 — server

CRITICALFix: kongchuanhujiao/server@9a12562

CVE-2021-21403 is a critical-severity (CVSS 9.8) CWE-305 vulnerability in github.com/kongchuanhujiao/server. A fix is available for github.com/kongchuanhujiao/server — see the affected versions and patch details below.

Authentication Bypass by Primary Weakness in github.com/kongchuanhujiao/server

Also known asGHSA-8wrg-m8vm-5fvj

Published

Mar 26, 2021

Updated

Jul 8, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs71th percentile — riskier than 71% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-21403 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

🐹github.com/kongchuanhujiao/server

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

Description

In github.com/kongchuanhujiao/server before version 1.3.21 there is an authentication Bypass by Primary Weakness vulnerability. All users are impacted. This is fixed in version 1.3.21.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/kongchuanhujiao/server`	all versions	1.3.21`go get github.com/kongchuanhujiao/server@v1.3.21`

Affected Products

1 product · 1 configurations

Application

kongchuanhujiaokongchuanhujiao_project

< 1.3.21

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/kongchuanhujiao/server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/kongchuanhujiao/server to 1.3.21 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-21403 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

In github.com/kongchuanhujiao/server before version 1.3.21 there is an authentication Bypass by Primary Weakness vulnerability. All users are impacted. This is fixed in version 1.3.21.

O3 Security · Impact-Aware SCA

Is CVE-2021-21403 in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

9.8/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE Classification

CWE-305CWE-305 CWE-287Improper Authentication

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

server

2.9/10

Code-Review0/10

Maintained0/10

Branch-Protection0/10

Assessed Oct 5, 2026

Timeline

Disclosed

Mar 26, 2021

Last updated

Jul 8, 2026

Identifiers

CVE-2021-21403

GHSA-8wrg-m8vm-5fvj

References

Advisorygithub.com Advisorynvd.nist.gov Fixgithub.com

Related vulnerabilities

This CVE is critical severity; 2 of 8 other CVEs with CWE-305 are rated as high or higher (top: critical).

CVE-2026-41052CVE-2026-9798CVE-2026-6334CVE-2026-2652CVE-2026-30849CVE-2026-33496CVE-2026-32730CVE-2026-3047Browse all CWE-305

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedJul 8, 2026

CVE-2021-21403 — server

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-21403 in your dependencies?