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Fencer Vulns
low 3.5

CVE-2023-22489 json

Flarum is missing authorization in discussion replies

published 2023-01-10 3 y ago modified 2026-06-17 4 mo ago also GHSA-hph3-hv3c-7725 , EUVD-2023-0489

cvss
3.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 47%
public exploits
0
none known

Summary

Flarum is a discussion platform for websites. 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 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. 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. The vulnerability has been fixed and published as flarum/core v1.6.3. All communities running Flarum should upgrade as soon as possible. There are no known workarounds.

Patch / fix

  • packagist flarum/core 1.6.3
  • flarum flarum 1.6.2

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
19 mo ago

Exploit prediction

0.58% chance of exploitation in the next 30 days, higher than 47% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
NVD 3.1 3.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
GitHub 3.1 3.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

Affected packages

ecosystem package affected fixed in
packagist flarum/core
>=1.3.0, <1.6.3
1.6.3

Affected products

  • flarum framework

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.