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CVE-2026-27468— Mastodon may allow unconfirmed FASP to make subscriptions

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 4.4.0版本至4.4.13版本和4.5.0版本至4.5.6版本存在安全漏洞，该漏洞源于FASP在订阅账户内容生命周期事件或回填内容时未正确检查是否已获批准，可能导致未经批准的订阅和回填请求，引发拒绝服务攻击。

AI Predicted 5.3 Difficulty: Easy EPSS 0.43% · P35
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I. Basic Information for CVE-2026-27468

Vulnerability Information
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Vulnerability Title
Mastodon may allow unconfirmed FASP to make subscriptions
Source: CVE Program / CVE List V5
Vulnerability Description
Mastodon is a free, open-source social network server based on ActivityPub. FASP registration requires manual approval by an administrator. In versions 4.4.0 through 4.4.13 and 4.5.0 through 4.5.6, actions performed by a FASP to subscribe to account/content lifecycle events or to backfill content did not check properly whether the FASP was actually approved. This only affects Mastodon servers that have opted in to testing the experimental FASP feature by setting the environment variable `EXPERIMENTAL_FEATURES` to a value including `fasp`. An attacker can make subscriptions and request content backfill without approval by an administrator. Done once, this leads to minor information leak of URIs that are publicly available anyway. But done several times this is a serious vector for DOS, putting pressure on the sidekiq worker responsible for the `fasp` queue. The fix is included in the 4.4.14 and 4.5.7 releases. Admins that are actively testing the experimental "fasp" feature should update their systems. Servers not using the experimental feature flag `fasp` are not affected.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:U
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
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 4.4.0版本至4.4.13版本和4.5.0版本至4.5.6版本存在安全漏洞，该漏洞源于FASP在订阅账户内容生命周期事件或回填内容时未正确检查是否已获批准，可能导致未经批准的订阅和回填请求，引发拒绝服务攻击。
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 >= 4.4.0, < 4.4.14 -

II. Public POCs for CVE-2026-27468

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III. Intelligence Information for CVE-2026-27468

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IV. Related Vulnerabilities

Same product: mastodon
Same vendor: mastodon
Same weakness: CWE-862

V. Comments for CVE-2026-27468

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