How severe is CVE-2021-3963?

CVE-2021-3963 has a CVSS score of 4.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-3963?

CVE-2021-3963 affects the following packages: kevinpapst/kimai2 (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-3963?

Update kevinpapst/kimai2 to 1.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3963 is resolved across your whole dependency graph.

How do I detect CVE-2021-3963 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for kevinpapst/kimai2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-3963 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-2021-3963 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-3963, 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-2021-3963?

CVE-2021-3963 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-2021-3963?

CVE-2021-3963 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-2021-3963 published, and has it been updated?

CVE-2021-3963 was published on November 19, 2021 and was last updated on October 20, 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-2021-3963 — kimai2

MEDIUMFix: kevinpapst/kimai2@95796ab

CVE-2021-3963 is a medium-severity (CVSS 4.3) Cross-Site Request Forgery (CSRF) vulnerability in kevinpapst/kimai2. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for kevinpapst/kimai2 — see the affected versions and patch details below.

Cross-site Scripting in kimai2

Also known asGHSA-gf2c-93hm-r9j5

Published

Nov 19, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Nov 5, 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

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐘kevinpapst/kimai2

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

kimai2 is vulnerable to Cross-Site Request Forgery (CSRF) in deleting invoice templates. This vulnerability is capable of tricking admin user to delete invoice templates.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`kevinpapst/kimai2`	all versions	1.16`composer require kevinpapst/kimai2:^1.16`

Affected Products

1 product · 1 configurations

Application

kimai 2kimai

< 1.16.2

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.

kimai2 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 kevinpapst/kimai2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update kevinpapst/kimai2 to 1.16 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3963 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

kimai2 is vulnerable to Cross-Site Request Forgery (CSRF) in deleting invoice templates. This vulnerability is capable of tricking admin user to delete invoice templates.

O3 Security · Impact-Aware SCA

Is CVE-2021-3963 in your dependencies?

Find it across Packagist, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

4.3/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

Raw vector

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

CWE Classification

CWE-352Cross-Site Request Forgery (CSRF)

Weaponization

No Nuclei template or Metasploit module yet. 1 public proof-of-concept reference is listed on this page.

OpenSSF Scorecard

Package health score

kimai2

5.9/10

Code-Review1/10

Maintained10/10

Branch-ProtectionN/A

Assessed Oct 26, 2026

Timeline

Disclosed

Nov 19, 2021

First exploit

Nov 23, 2021

4 days after disclosure — rapid exploitation

Last updated

Oct 20, 2026

Identifiers

CVE-2021-3963

GHSA-gf2c-93hm-r9j5

References

Advisorynvd.nist.gov · CVE 2021 3963 Fixgithub.com · 95796ab2560ad93f44068a88f0fad758c2053514 Fixhuntr.dev · 3abf308b 7dbd 4864 b1a9 5c45b876def8

Related vulnerabilities

This CVE is medium severity; 8 of 8 other CVEs affecting kevinpapst/kimai2 are rated as high or higher (top: high).

CVE-2019-15481CVE-2021-43515CVE-2021-4033CVE-2021-3983CVE-2021-3992CVE-2021-3985CVE-2021-3957CVE-2021-3976

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 20, 2026

CVE-2021-3963 — kimai2

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-2021-3963 in your dependencies?