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CVE-2026-23961

nvd nist
Published: Jan 22, 2026Modified: Jun 17, 2026

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5.3
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Exploitability: 3.9 / Impact: 1.4
Source: security-advisories@github.com (Secondary)

Description

Mastodon is a free, open-source social network server based on ActivityPub. Mastodon allows server administrators to suspend remote users to prevent interactions. However, some logic errors allow already-known posts from such suspended users to appear in timelines if boosted. Furthermore, under certain circumstances, previously-unknown posts from suspended users can be processed. This issue allows old posts from suspended users to occasionally end up on timelines on all Mastodon versions. Additionally, on Mastodon versions from v4.5.0 to v4.5.4, v4.4.5 to v4.4.11, v4.3.13 to v4.3.17, and v4.2.26 to v4.2.29, remote suspended users can partially bypass the suspension to get new posts in. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.

Affected (3)

Joinmastodon
1 product
Mastodon
Configuration A
3 vulnerable
Vulnerable SoftwareAffected Versions
Joinmastodon
Mastodon
Before 4.3.18
Mastodon
From 4.4.0 to 4.4.12
Mastodon
From 4.5.0 to 4.5.5

Related CWEs

CWE-863
Incorrect Authorization
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.

References (4)

Source: security-advisories@github.com
Release Notes
Source: security-advisories@github.com
Release Notes
Source: security-advisories@github.com
Release Notes
Source: security-advisories@github.com
Vendor Advisory

Timeline

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