Flarum vulnerable to LFI and Blind SSRF via Avatar upload

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2023-40033: 0.50% estimated exploitation activity in the next 30 days; percentile 43.18 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The Flarum forum software is affected by a vulnerability that allows an attacker to conduct a Blind SSRF attack or disclose any file on the server, even with a basic user account on any Flarum forum. By uploading a file containing a URL and spoofing the MIME type, an attacker can manipulate the application to execute unintended actions. The vulnerability is due to the behavior of the intervention/image package, which attempts to interpret the supplied file contents as a URL, which then fetches its contents. This allows an attacker to exploit the vulnerability to perform SSRF attacks, disclose local file contents, or conduct a blind oracle attack. Patches This has been patched in Flarum v1.8. Workarounds As a temporary workaround for the SSRF aspect of the vulnerability, one can disable PHP's allowurlfopen which will prevent the fetching of external files via URLs. Credits Adam Kues - Assetnote

Published by the source

16 Aug 2023, 21:02 UTC

Last modified by the source

9 Nov 2023, 05:05 UTC

Source last checked

26 Oct 2026, 14:10 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-67c6-q4j4-hccg

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# Patch Next advisory brief: CVE-2023-40033

Advisory: Flarum vulnerable to LFI and Blind SSRF via Avatar upload
IDs: CVE-2023-40033, GHSA-67c6-q4j4-hccg
Record: https://patchnext.com/advisories/cve-2023-40033 (revision 1, source checked 26 Oct 2026, 14:10 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: flarum/framework 1.8.0; flarum/core 1.8.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist flarum/framework: affected < 1.8.0; fixed in 1.8.0
- Packagist flarum/core: affected < 1.8.0; fixed in 1.8.0

## Suggested inspection (read-only)
- Packagist flarum/framework: check the installed version with your package manager.
- Packagist flarum/core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on flarum/framework, flarum/core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-67c6-q4j4-hccg (GitHub-reviewed advisory GHSA-67c6-q4j4-hccg lists affected ranges: Packagist flarum/core >=0 =0 <1.8.0)

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