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.

Severity

 

CVSS Version 3.x CVSS Version 2.0

CVSS 3.x Severity and Metrics:

CNA:  GitHub, Inc.

Base Score:  3.5 LOW

Vector:  CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: The NVD and the CNA have provided the same score. When this occurs only the CNA information is displayed, but the Acceptance Level icon for the CNA is given a checkmark to signify NVD concurrence.

CVSS 2.0 Severity and Metrics:

NIST: NVD

Base Score: N/A

NVD score not yet provided.

NVD Analysts use publicly available information to associate vector strings and CVSS scores. We also display any CVSS information provided within the CVE List from the CNA.

Note: NVD Analysts have not published a CVSS score for this CVE at this time. NVD Analysts use publicly available information at the time of analysis to associate CVSS vector strings.

References to Advisories, Solutions, and Tools

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Hyperlink	Resource
https://github.com/flarum/framework/commit/12f14112a0ecd1484d97330b82beb2a145919015	Patch  Third Party Advisory
https://github.com/flarum/framework/releases/tag/v1.6.3	Release Notes  Third Party Advisory
https://github.com/flarum/framework/security/advisories/GHSA-hph3-hv3c-7725	Mitigation  Third Party Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-862	Missing Authorization	GitHub, Inc.

Known Affected Software Configurations Switch to CPE 2.2

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Change History

1 change records found show changes

Initial Analysis by NIST 1/23/2023 12:55:21 PM

Action	Type	Old Value	New Value
Added	CPE Configuration		OR *cpe:2.3:a:flarum:flarum:*:*:*:*:*:*:*:* versions from (including) 1.3.0 up to (excluding) 1.6.2
Added	CVSS V3.1		NIST AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Changed	Reference Type	https://github.com/flarum/framework/commit/12f14112a0ecd1484d97330b82beb2a145919015 No Types Assigned	https://github.com/flarum/framework/commit/12f14112a0ecd1484d97330b82beb2a145919015 Patch, Third Party Advisory
Changed	Reference Type	https://github.com/flarum/framework/releases/tag/v1.6.3 No Types Assigned	https://github.com/flarum/framework/releases/tag/v1.6.3 Release Notes, Third Party Advisory
Changed	Reference Type	https://github.com/flarum/framework/security/advisories/GHSA-hph3-hv3c-7725 No Types Assigned	https://github.com/flarum/framework/security/advisories/GHSA-hph3-hv3c-7725 Mitigation, Third Party Advisory