GHSA-22m9-m3ww-53h3 · Severity: high · Ecosystem: composer — Flarum post mentions can be used to read any post on the forum without access control
Flarum is a forum software for building communities. Using the mentions feature provided by the flarum/mentions extension, users can mention any post ID on the forum with the special `@"<username>"#p<id>` syntax. The following behavior never changes no matter if the actor should be able to read the mentioned post or not: A URL to the mentioned post is inserted into the actor post HTML, leaking its discussion ID and post number. The `mentionsPosts` relationship included in the `POST /api/posts` and `PATCH /api/posts/<id>` JSON responses leaks the full JSON:API payload of all mentioned posts without any access control. This includes the content, date, number and attributes added by other extensions. An attacker only needs the ability to create new posts on the forum to exploit the vulnerability. This works even if new posts require approval. If they have the ability to edit posts, the attack can be performed even more discreetly by using a single post to scan any size of database and hiding the attack post content afterward. The attack allows the leaking of all posts in the forum database, including posts awaiting approval, posts in tags the user has no access to, and private discussions created by other extensions like FriendsOfFlarum Byobu. This also includes non-comment posts like tag changes or renaming events. The discussion payload is not leaked but using the mention HTML payload it's possible to extract the discussion ID of all posts and combine all posts back together into their original discussions even if the discussion title remains unknown. All Flarum versions prior to 1.6.3 are affected. The vulnerability has been fixed and published as flarum/core v1.6.3. As a workaround, user can disable the mentions extension.
Conclusion & alert: CVE-2023-22487 is rated High Exploit Risk (60.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.21%). Core evidence: 1 public exploit reference(s) are indexed (Exploit-DB). Mandatory action: Public exploits are available—assess exposure, apply mitigations, and prioritize patching.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
| EDB-ID | Source | Kind | Published | Link |
|---|---|---|---|---|
| — | nvd_ref | exploit_tag | Exploit-DB ↗ |
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-01-21 | 0.25% | 0.21% | -0.04% |
| 2 | 2026-01-12 | 0.09% | 0.25% | +0.16% |
| 3 | 2025-11-21 | — | 0.09% | — |
Full EPSS history (11 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 7.7 | 3.1 | HIGH |
|
3.1 | 4.0 | [email protected] |
| 4.3 | 3.1 | MEDIUM |
|
2.8 | 1.4 | [email protected] |
GHSA-22m9-m3ww-53h3 · Severity: high · Ecosystem: composer — Flarum post mentions can be used to read any post on the forum without access control
| URL | Tags |
|---|---|
| https://github.com/flarum/framework/commit/ab1c868b978e8b0d09a5d682c54665dae17d0985 | Patch Third Party Advisory |
| https://github.com/flarum/framework/security/advisories/GHSA-22m9-m3ww-53h3 | Exploit Mitigation Third Party Advisory |