CVE-2023-22489 is a low-severity (CVSS 3.5) CWE-862 vulnerability in flarum/core. A fix is available for flarum/core — see the affected versions and patch details below.
Flarum is missing authorization in discussion replies
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2023-22489.
EPSS Exploitation Probability
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.
How urgent is this, really
CVE-2023-22489 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
flarum/coreReal-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
If the first post of a discussion is permanently deleted but the discussion stays visible, any actor who can view the discussion is able to create a new reply via the REST API, no matter the reply permission or lock status.
This includes users that don't have a validated email.
Guests cannot successfully create a reply because the API will fail with a 500 error when the user ID 0 is inserted into the database. This should also be fixed to return the expected 401/403 status.
This happens because when the first post of a discussion is permanently deleted, the first_post_id attribute of the discussion becomes null which causes access control to be skipped for all new replies.
Flarum automatically makes discussions with zero comments invisible so an additional condition for this vulnerability is that the discussion must have at least one approved reply so that discussions.comment_count is still above zero after the post deletion.
Impact
This can open the discussion to uncontrolled spam or just unintentional replies if users still had their tab open before the vulnerable discussion was locked and then post a reply when they shouldn't be able to.
In combination with the email notification settings, this could also be used as a way to send unsolicited emails.
Versions between v1.3.0 and v1.6.3 are impacted.
Patches
The vulnerability has been fixed and published as flarum/core v1.6.3. All communities running Flarum should upgrade as soon as possible to v1.6.3 using:
composer update --prefer-dist --no-dev -a -W
You can then confirm you run the latest version using:
composer show flarum/core
Workarounds
If you don't delete the first posts you are not affected. A workaround can be to delete the discussion itself, or amend the database to manually set a first_post_id.
For more information
For any questions or comments on this vulnerability please visit https://discuss.flarum.org/
For support questions create a discussion at https://discuss.flarum.org/t/support.
A reminder that if you ever become aware of a security issue in Flarum, please report it to us privately by emailing [email protected], and we will address it promptly.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | flarum/core | ≥ 1.3.0&&< 1.6.3 | 1.6.3composer require flarum/core:^1.6.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for flarum/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update flarum/core to 1.6.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-22489 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 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-22489 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-22489. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-22489 in your dependencies?
O3 Security finds CVE-2023-22489 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.