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CVE-2026-22246— Local Mastodon users can enumerate and access severed relationships of every other local user

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 4.3.17之前版本、4.4.11之前版本和4.5.4之前版本存在安全漏洞，该漏洞源于缺少关系列表所有权检查，可能导致信息泄露。

CVSS 6.5 · Medium EPSS 0.26% · P16

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage
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I. Basic Information for CVE-2026-22246

Vulnerability Information
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Vulnerability Title
Local Mastodon users can enumerate and access severed relationships of every other local user
Source: CVE Program / CVE List V5
Vulnerability Description
Mastodon is a free, open-source social network server based on ActivityPub. Mastodon 4.3 added notifications of severed relationships, allowing end-users to inspect the relationships they lost as the result of a moderation action. The code allowing users to download lists of severed relationships for a particular event fails to check the owner of the list before returning the lost relationships. Any registered local user can access the list of lost followers and followed users caused by any severance event, and go through all severance events this way. The leaked information does not include the name of the account which has lost follows and followers. This has been fixed in Mastodon v4.3.17, v4.4.11 and v4.5.4.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过发送数据的信息暴露
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 4.3.17之前版本、4.4.11之前版本和4.5.4之前版本存在安全漏洞，该漏洞源于缺少关系列表所有权检查，可能导致信息泄露。
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 < 4.3.17 -

II. Public POCs for CVE-2026-22246

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III. Intelligence Information for CVE-2026-22246

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IV. Related Vulnerabilities

Same product: mastodon
Same vendor: mastodon
Same weakness: CWE-201

V. Comments for CVE-2026-22246

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