How severe is CVE-2023-40033?

CVE-2023-40033 has a CVSS score of 7.1/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2023-40033?

CVE-2023-40033 affects the following packages: flarum/core (Packagist), flarum/framework (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2023-40033?

Update flarum/core to 1.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-40033 is resolved across your whole dependency graph.

How do I detect CVE-2023-40033 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flarum/core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2023-40033 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2023-40033?

O3 pinpoints whether CVE-2023-40033 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2023-40033 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-40033 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-40033?

CVE-2023-40033 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 34th 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.

When was CVE-2023-40033 published, and has it been updated?

CVE-2023-40033 was published on August 16, 2023 and was last updated on April 10, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2023-40033: Server-Side Request Forgery via Avatar upload i…

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk34th percentile+0.23%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

2 pkgs affected

🐘flarum/core🐘flarum/framework

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

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.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`flarum/core`	all versions	1.8.0
🐘Packagist	`flarum/framework`	all versions	1.8.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flarum/core. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update flarum/core to 1.8.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-40033 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2023-40033 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2023-40033. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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 exploi

O3 Security · Impact-Aware SCA

Is CVE-2023-40033 in your dependencies?

O3 detects CVE-2023-40033 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

CVE-2023-40033