How severe is CVE-2021-3846?

CVE-2021-3846 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-3846?

CVE-2021-3846 affects the following packages: grumpydictator/firefly-iii (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-3846?

Update grumpydictator/firefly-iii to 5.6.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3846 is resolved across your whole dependency graph.

How do I detect CVE-2021-3846 in my Packagist dependencies?

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

How do I mitigate CVE-2021-3846 if there is no patch (or I can't update yet)?

Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

Is CVE-2021-3846 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-3846, 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-2021-3846?

CVE-2021-3846 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 56th 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-2021-3846?

CVE-2021-3846 is classified as Unrestricted File Upload (CWE-434). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-3846 published, and has it been updated?

CVE-2021-3846 was published on October 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

HIGH severity

CVE-2021-3846 — firefly-iii

HIGHFix: firefly-iii/firefly-iii@a85b642

CVE-2021-3846 is a high-severity (CVSS 8.8) Unrestricted File Upload vulnerability in grumpydictator/firefly-iii. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for grumpydictator/firefly-iii — see the affected versions and patch details below.

Unrestricted File Upload vulnerability in Firefly III

Also known asGHSA-5gq7-826w-8282

Published

Oct 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 ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs56th percentile — riskier than 56% 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

🐘grumpydictator/firefly-iii

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

firefly-iii is vulnerable to Unrestricted Upload of File with Dangerous Type

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`grumpydictator/firefly-iii`	all versions	5.6.2`composer require grumpydictator/firefly-iii:^5.6.2`

Affected Products

1 product · 1 configurations

Application

firefly iiifirefly-iii

< 5.6.2

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.

firefly-iii is vulnerable to Unrestricted Upload of File with Dangerous …

huntr.devNVDOct 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for grumpydictator/firefly-iii, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update grumpydictator/firefly-iii to 5.6.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3846 is resolved across your whole dependency graph.
Workarounds
Treat uploaded files as untrusted until proven otherwise: validate the actual content type rather than the supplied extension, store uploads outside the web root on a volume mounted without execute permission, and rename them to server-generated identifiers so an attacker cannot choose the path a request will later resolve.

Frequently Asked Questions

firefly-iii is vulnerable to Unrestricted Upload of File with Dangerous Type

O3 Security · Impact-Aware SCA

Is CVE-2021-3846 in your dependencies?

Find it across Packagist, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

8.8/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Raw vector

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

CWE Classification

CWE-434Unrestricted File Upload

Weaponization

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

OpenSSF Scorecard

Package health score

firefly-iii

4.6/10

Maintained10/10

Code-Review0/10

Branch-Protection3/10

Assessed Oct 19, 2026

Timeline

Disclosed

Oct 19, 2021

First exploit

Oct 22, 2021

2 days after disclosure — rapid exploitation

Last updated

Oct 20, 2026

Identifiers

CVE-2021-3846

GHSA-5gq7-826w-8282

References

Advisorynvd.nist.gov · CVE 2021 3846 Fixgithub.com · a85b6420c19ace35134f896e094e1971d8c7954b Fixhuntr.dev · 5267ec1c d204 40d2 bd4f 6c2dd495ee18

Related vulnerabilities

This CVE is high severity; 1 of 8 other CVEs affecting grumpydictator/firefly-iii is rated as high or higher (top: critical).

CVE-2026-50886GHSA-6jq6-x4cx-qvcmGHSA-5q8v-j673-m5v4CVE-2024-37893GHSA-29w6-c52g-m8jcCVE-2024-22075CVE-2023-1788CVE-2023-1789

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 20, 2026

CVE-2021-3846 — firefly-iii

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-2021-3846 in your dependencies?