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Vulnerability record · CVE-2023-40033 · published 16 August 2023

CVE-2023-40033: Flarum server-side request forgery (ssrf) vulnerability

Flarum · Flarum

Flarum is an open source forum software. Flarum is affected by a vulnerability that allows an attacker to conduct a Blind Server-Side Request Forgery (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. This has been patched in Flarum version 1.8.0. Users are advised to upgrade. Users unable to upgrade may disable PHP's `allow_url_fopen` which will prevent the fetching of external files via URLs as a temporary workaround for the SSRF aspect of the vulnerability.

7.1 CVSS 3.1 High EPSS 0.50% · top 59.6% CWE-918 · Server-side request forgery (SSRF)
7.1CVSS 3.1 base score
0.50%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References
17 Jun 2026Last modified by NVD

Description

Flarum is an open source forum software. Flarum is affected by a vulnerability that allows an attacker to conduct a Blind Server-Side Request Forgery (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. This has been patched in Flarum version 1.8.0. Users are advised to upgrade. Users unable to upgrade may disable PHP's `allow_url_fopen` which will prevent the fetching of external files via URLs as a temporary workaround for the SSRF aspect of the vulnerability.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/flarum/framework/commit/d1059c1cc79fe61f9538f3da55e8f42abbede570 Patch
https://github.com/flarum/framework/security/advisories/GHSA-67c6-q4j4-hccg Vendor Advisory
https://github.com/flarum/framework/commit/d1059c1cc79fe61f9538f3da55e8f42abbede570 Patch
https://github.com/flarum/framework/security/advisories/GHSA-67c6-q4j4-hccg Vendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2021-32671Flarum cross-site scripting vulnerabilityFlarum is a forum software for building communities. Flarum's translation system allowed for string inputs to be converted into HTML DOM nodes when r…EPSS 40%8.8CVE-2019-13183Flarum cross-site request forgery vulnerabilityFlarum before 0.1.0-beta.9 allows CSRF against all POST endpoints, as demonstrated by changing admin settings.EPSS 0.79%7.5CVE-2019-11514Flarum vulnerabilityUser/Command/ConfirmEmailHandler.php in Flarum before 0.1.0-beta.8 mishandles invalidation of user email tokens.EPSS 1.3%6.8CVE-2025-27794Flarum injection vulnerabilityFlarum is open-source forum software. A session hijacking vulnerability exists in versions prior to 1.8.10 when an attacker-controlled authoritative …EPSS 0.49%5.4CVE-2023-22488Flarum missing authorization vulnerabilityFlarum is a forum software for building communities. Using the notifications feature, one can read restricted/private content and bypass access check…EPSS 0.40%5.4CVE-2022-41938Flarum cross-site scripting vulnerabilityFlarum is an open source discussion platform. Flarum's page title system allowed for page titles to be converted into HTML DOM nodes when pages were …EPSS 0.74%5.3CVE-2018-19133Flarum information exposure vulnerabilityIn Flarum Core 0.1.0-beta.7.1, a serious leak can get everyone's email address.EPSS 1.2%4.9CVE-2023-27577Flarum path traversal vulnerabilityflarum is a forum software package for building communities. In versions prior to 1.7.0 an admin account which has already been compromised by an att…EPSS 0.85%

Source: NIST National Vulnerability Database (record CVE-2023-40033), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.