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CVE-2026-23964— Mastodon has insufficient access control to push notification settings

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 v4.5.5之前版本、v4.4.12之前版本和v4.3.18之前版本存在安全漏洞，该漏洞源于Web推送订阅更新端点存在不安全的直接对象引用，可能导致推送通知被破坏和信息泄露。

CVSS 6.5 · Medium EPSS 0.23% · P12
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I. Basic Information for CVE-2026-23964

Vulnerability Information
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Vulnerability Title
Mastodon has insufficient access control to push notification settings
Source: CVE Program / CVE List V5
Vulnerability Description
Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.5.5, 4.4.12, and 4.3.18, an insecure direct object reference in the web push subscription update endpoint lets any authenticated user update another user's push subscription by guessing or obtaining the numeric subscription id. This can be used to disrupt push notifications for other users and also leaks the web push subscription endpoint. Any user with a web push subscription is impacted, because another authenticated user can tamper with their push subscription settings if they can guess or obtain the subscription id. This allows an attacker to disrupt push notifications by changing the policy (whether to filter notifications from non-followers or non-followed users) and subscribed notification types of their victims. Additionally, the endpoint returns the subscription object, which includes the push notification endpoint for this subscription, but not its keypair. 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:L/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 v4.5.5之前版本、v4.4.12之前版本和v4.3.18之前版本存在安全漏洞，该漏洞源于Web推送订阅更新端点存在不安全的直接对象引用，可能导致推送通知被破坏和信息泄露。
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 < 4.3.18 -

II. Public POCs for CVE-2026-23964

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III. Intelligence Information for CVE-2026-23964

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Vendor Advisories for CVE-2026-23964 (1)

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-2026-23961 5.3 MEDIUM Mastodon may allow a remote suspension bypass
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-2026-23964

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