Summary
Flarum notifications can leak restricted content
Using the notifications feature, one can read restricted/private content and bypass access checks that would be in place for such content.
The notification-sending component does not check that the subject of the notification can be seen by the receiver, and proceeds to send notifications through their different channels. The alerts do not leak data despite this as they are listed based on a visibility check, however, emails are still sent out.
This means that, for extensions which restrict access to posts, any actor can bypass the restriction by subscribing to the discussion if the Subscriptions extension is enabled.
Workarounds
Disable the Flarum Subscriptions extension or disable email notifications altogether.
There is no other supported workaround for this issue for Flarum versions below 1.6.3.
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.
Impact
The attack allows the leaking of some posts in the forum database, including posts awaiting approval, posts in tags the user has no access to if they could subscribe to a discussion before it becomes private, and posts restricted by third-party extensions.
Other leaks could also happen for different notification subjects if some features allowed to receive specific types of notifications for restricted content.
All Flarum versions prior to v1.6.3 are affected.
The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.
CVE-2023-22488 has a CVSS score of 6.8 (Medium). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.6.3); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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See it in your environmentNew to Kodem? Get a demo →Remediation advice
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
Frequently Asked Questions
- What is CVE-2023-22488? CVE-2023-22488 is a medium-severity missing authorization vulnerability in flarum/core (composer), affecting versions < 1.6.3. It is fixed in 1.6.3. The application does not perform an authorization check before performing a sensitive operation.
- How severe is CVE-2023-22488? CVE-2023-22488 has a CVSS score of 6.8 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of flarum/core are affected by CVE-2023-22488? flarum/core (composer) versions < 1.6.3 is affected.
- Is there a fix for CVE-2023-22488? Yes. CVE-2023-22488 is fixed in 1.6.3. Upgrade to this version or later.
- Is CVE-2023-22488 exploitable, and should I be worried? Whether CVE-2023-22488 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2023-22488 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2023-22488? Upgrade
flarum/coreto 1.6.3 or later.