CVE-2026-50886: Grumpydictator/firefly iii Project Firefly III Has Incorrect Vulnerability

CRITICAL
Advisory Identifier: GHSA-9mmg-q95p-gp67
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CVSS 9.1
CWE-284
Published
Advisory Summary

CVE-2026-50886 is a CRITICAL (CVSS 9.1) project firefly iii has incorrect vulnerability (CWE-284: Improper Access Control) affecting Grumpydictator/firefly iii libraries in the Packagist ecosystem. The issue involves project firefly iii has incorrect access control in the webhook management component. Remediation is available in the latest vendor maintenance releases.

CVE-2026-50886 at a Glance

CVE Identifier CVE-2026-50886
GHSA Identifier GHSA-9mmg-q95p-gp67
Severity CRITICAL
CVSS v3.1 Base Score 9.1
CWE Classification CWE-284: Improper Access Control
Affected Product Grumpydictator/firefly iii
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 9.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-50886

To remediate this vulnerability, upgrade all affected Grumpydictator/firefly iii dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

grumpydictator/firefly-iii fixed: Latest secure release 
Upgrade grumpydictator/firefly-iii to Latest secure release
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for grumpydictator/firefly-iii

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-50886, inspect your project dependencies for Grumpydictator/firefly iii:

inspect dependencies for grumpydictator/firefly-iii

Analyze the terminal output to locate any version of Grumpydictator/firefly iii in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. In Grumpydictator/firefly iii, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

Incorrect access control in the webhook management component of Project Firefly III v6.5.9 allows attackers to scan internal resources via a crafted POST request.

CVE-2026-50886 Affected Grumpydictator/firefly iii Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
grumpydictator/firefly-iii
 Packagist
≤ 6.5.9

References

NVD — CVE-2026-50886 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-50886
Grumpydictator/firefly iii Source Repository REPOSITORY
https://gist.github.com/pyuysig/f5395f90753ba652835ba9c6abf4c4ae
Grumpydictator/firefly iii Source Repository REPOSITORY
https://github.com/firefly-iii/firefly-iii

Frequently Asked Questions

What is CVE-2026-50886?
CVE-2026-50886 is a security vulnerability in Grumpydictator/firefly iii involving Project Firefly III has incorrect access control in the webhook management component under CWE-284: Improper Access Control.
Which Grumpydictator/firefly iii versions are affected?
Affected versions include releases prior to current release patches across affected packages: grumpydictator/firefly-iii.
What version fixes CVE-2026-50886?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is grumpydictator/firefly-iii affected?
Yes, grumpydictator/firefly-iii is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2026-50886?
CVE-2026-50886 has a CVSS v3.1 base score of 9.1 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.
What CWE is associated with CVE-2026-50886?
CVE-2026-50886 is classified under CWE-284: Improper Access Control (The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.).
How can I check Packagist dependencies for CVE-2026-50886?
Run the dependency tree command: 'inspect dependencies for grumpydictator/firefly-iii'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-9mmg-q95p-gp67",
  "modified" : "2026-08-27T16:41:21Z",
  "published" : "2026-06-15T21:30:41Z",
  "aliases" : [ "CVE-2026-50886" ],
  "summary" : "Project Firefly III has incorrect access control in the webhook management component",
  "details" : "Incorrect access control in the webhook management component of Project Firefly III v6.5.9 allows attackers to scan internal resources via a crafted POST request.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "grumpydictator/firefly-iii"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "6.5.9"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-50886"
  }, {
    "type" : "WEB",
    "url" : "https://gist.github.com/pyuysig/f5395f90753ba652835ba9c6abf4c4ae"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/firefly-iii/firefly-iii"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-284" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-27T16:41:21Z",
    "nvd_published_at" : "2026-06-15T20:16:31Z"
  }
}