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CVE-2023-22489

Flarum is missing authorization in discussion replies

LOW
3.5
CVSS Score
Published: January 13, 2023 at 06:03 PM UTC
Updated: June 17, 2026 at 05:35 AM UTC
1 product affected across 1 vendorFlarum

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Severity
LOW3.5
Exploit prediction
EPSS 0.6%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Flarum· Flarumcomposer
95%
v < 1.6.31.3.0 ≤ v < 1.6.2
Affected range stops below 1.6.2, so it looks safe — our inference, not a vendor statement
Affected range stops below 1.6.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

References (3)

x_refsource_MISCPatchThird Party Advisory
Source: [email protected]
https://github.com/flarum/framework/commit/12f14112a0ecd1484d97330b82beb2a145919015
x_refsource_MISCRelease NotesThird Party Advisory
Source: [email protected]
https://github.com/flarum/framework/releases/tag/v1.6.3
x_refsource_CONFIRMMitigationThird Party Advisory
Source: [email protected]
https://github.com/flarum/framework/security/advisories/GHSA-hph3-hv3c-7725

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

3.5LOWGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-862

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