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CVE-2026-23961— Mastodon may allow a remote suspension bypass

Quick assessment

Affected
mastodon mastodon
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Mastodon是Mastodon开源的一款基于ActivityPub的开源社交网络服务器。 Mastodon存在安全漏洞，该漏洞源于逻辑错误允许被暂停用户的旧帖子出现在时间线上，在特定版本中可能部分绕过暂停。

CVSS 5.3 · Medium EPSS 0.45% · P37

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage
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I. Basic Information for CVE-2026-23961

Vulnerability Information
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Vulnerability Title
Mastodon may allow a remote suspension bypass
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制不正确
Source: CVE Program / CVE List V5
Vulnerability Title
Mastodon 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mastodon是Mastodon开源的一款基于ActivityPub的开源社交网络服务器。 Mastodon存在安全漏洞，该漏洞源于逻辑错误允许被暂停用户的旧帖子出现在时间线上，在特定版本中可能部分绕过暂停。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mastodon mastodon < 4.3.18 -

II. Public POCs for CVE-2026-23961

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III. Intelligence Information for CVE-2026-23961

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Same Patch Batch · mastodon · 2026-01-22 · 4 CVEs total

CVE-2026-23962 7.5 HIGH Mastodon vulnerable to Denial of Service from a single post (client/server)
CVE-2026-23964 6.5 MEDIUM Mastodon has insufficient access control to push notification settings
CVE-2026-23963 4.3 MEDIUM Mastodon missing length limits on list names, filter names, and filter keywords

IV. Related Vulnerabilities

Same product: mastodon
Same vendor: mastodon
Same weakness: CWE-863

V. Comments for CVE-2026-23961

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