🛡️ CVE-2023-40033 — flarum

🟠 CVSS 8.0 — High ✅ No Known Exploit CWE-918 NVD
8.0
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Flarum vulnerable to LFI and Blind SSRF via Avatar upload

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 allow_url_fopen which will prevent the fetching of external files via URLs.

Credits

Adam Kues - [Assetnote](https://assetnote.io/)

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity low, availability none.

Weakness class

CVE-2023-40033 is classified as CWE-918: Server-Side Request Forgery (SSRF). The server fetches a URL supplied by the caller, which can be pointed at internal systems it alone can reach.

Affected software

CVE-2023-40033 is recorded against 3 packages.

  • flarum (fixed in 1.8.0)
  • flarum/core (fixed in 1.8.0)
  • flarum/framework (fixed in 1.8.0)

Timeline and source

Published on 16 August 2023 and last revised on 17 June 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
github.com
github.com
github.com

Details

Severity HIGH
CVSS Score 8.0
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
CWE CWE-918
Public Exploit ✅ No
Source NVD
Published 2023-08-16
Updated 2026-08-12
Modified 2026-06-17

Affected Packages

Software From version Fixed in
flarum — 1.8.0
flarum/core — 1.8.0
flarum/framework — 1.8.0

Similar Threats

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