How severe is CVE-2021-3776?

CVE-2021-3776 has a CVSS score of 5.4/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-3776?

CVE-2021-3776 affects the following packages: showdoc/showdoc (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-3776?

Update showdoc/showdoc to 2.9.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3776 is resolved across your whole dependency graph.

How do I detect CVE-2021-3776 in my Packagist dependencies?

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

How do I mitigate CVE-2021-3776 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.

Is CVE-2021-3776 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-3776, including 1 in-the-wild exploitation 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 is the EPSS score for CVE-2021-3776?

CVE-2021-3776 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 34th 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-2021-3776?

CVE-2021-3776 is classified as Cross-Site Request Forgery (CSRF) (CWE-352). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-3776 published, and has it been updated?

CVE-2021-3776 was published on November 13, 2021 and was last updated on August 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

MEDIUM severity

CVE-2021-3776 — showdoc

MEDIUMFix: star7th/showdoc@67093c8

CVE-2021-3776 is a medium-severity (CVSS 5.4) Cross-Site Request Forgery (CSRF) vulnerability in showdoc/showdoc. 1 public exploit reference exists, so weaponization risk is real. A fix is available for showdoc/showdoc — see the affected versions and patch details below.

showdoc is vulnerable to Cross-Site Request Forgery (CSRF)

Also known asGHSA-m4hj-wg2r-qpcr

Published

Nov 13, 2021

Updated

Aug 7, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs34th percentile — riskier than 34% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-3776 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

🐘showdoc/showdoc

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

Description

showdoc is vulnerable to Cross-Site Request Forgery (CSRF)

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`showdoc/showdoc`	all versions	2.9.13`composer require showdoc/showdoc:^2.9.13`

Affected Products

1 product · 1 configurations

Application

showdocshowdoc

≤ 2.9.12

range

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.

showdoc is vulnerable to Cross-Site Request Forgery (CSRF)

huntr.devNVDNov 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for showdoc/showdoc, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update showdoc/showdoc to 2.9.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3776 is resolved across your whole dependency graph.
Workarounds
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.

Frequently Asked Questions

showdoc is vulnerable to Cross-Site Request Forgery (CSRF)

O3 Security · Impact-Aware SCA

Is CVE-2021-3776 in your dependencies?

Find it across Packagist, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

5.4/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

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

CWE Classification

CWE-352Cross-Site Request Forgery (CSRF)

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

showdoc

4.3/10

Maintained10/10

Code-Review1/10

Branch-Protection0/10

Assessed Oct 5, 2026

Timeline

Disclosed

Nov 13, 2021

First exploit

Nov 16, 2021

3 days after disclosure — rapid exploitation

Last updated

Aug 7, 2026

Identifiers

CVE-2021-3776

GHSA-m4hj-wg2r-qpcr

References

Advisorynvd.nist.gov Fixgithub.com Fixhuntr.dev Packagegithub.com

Related vulnerabilities

This CVE is medium severity; 8 of 8 other CVEs affecting showdoc/showdoc are rated as high or higher (top: critical).

CVE-2026-6982CVE-2025-0520CVE-2018-16342CVE-2018-19621CVE-2018-19609CVE-2018-19620CVE-2022-1034CVE-2022-0967

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedAug 7, 2026

CVE-2021-3776 — showdoc

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-2021-3776 in your dependencies?