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prionPRIOn knowledge basePRION:CVE-2024-23649
HistoryJan 24, 2024 - 6:15 p.m.

Design/Logic Flaw

2024-01-2418:15:00
PRIOn knowledge base
www.prio-n.com
6
lemmy
private message
api
security flaw
instance configuration
workaround
nvd

6.5 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

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

7 High

AI Score

Confidence

High

4 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

LOW

Authentication

SINGLE

Confidentiality Impact

PARTIAL

Integrity Impact

NONE

Availability Impact

NONE

AV:N/AC:L/Au:S/C:P/I:N/A:N

0.0005 Low

EPSS

Percentile

18.1%

Lemmy is a link aggregator and forum for the fediverse. Starting in version 0.17.0 and prior to version 0.19.1, users can report private messages, even when they’re neither sender nor recipient of the message. The API response to creating a private message report contains the private message itself, which means any user can just iterate over message ids to (loudly) obtain all private messages of an instance. A user with instance admin privileges can also abuse this if the private message is removed from the response, as they’re able to see the resulting reports.

Creating a private message report by POSTing to /api/v3/private_message/report does not validate whether the reporter is the recipient of the message. lemmy-ui does not allow the sender to report the message; the API method should likely be restricted to accessible to recipients only. The API response when creating a report contains the private_message_report_view with all the details of the report, including the private message that has been reported:

Any authenticated user can obtain arbitrary (untargeted) private message contents. Privileges required depend on the instance configuration; when registrations are enabled without application system, the privileges required are practically none. When registration applications are required, privileges required could be considered low, but this assessment heavily varies by instance.

Version 0.19.1 contains a patch for this issue. A workaround is available. If an update to a fixed Lemmy version is not immediately possible, the API route can be blocked in the reverse proxy. This will prevent anyone from reporting private messages, but it will also prevent exploitation before the update has been applied.

CPENameOperatorVersion
lemmyge0.17.0
lemmylt0.19.1

6.5 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

LOW

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

HIGH

Integrity Impact

NONE

Availability Impact

NONE

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

7 High

AI Score

Confidence

High

4 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

LOW

Authentication

SINGLE

Confidentiality Impact

PARTIAL

Integrity Impact

NONE

Availability Impact

NONE

AV:N/AC:L/Au:S/C:P/I:N/A:N

0.0005 Low

EPSS

Percentile

18.1%

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