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CVE-2026-23962— Mastodon vulnerable to Denial of Service from a single post (client/server)

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 v4.3.18之前版本、v4.4.12之前版本和v4.5.5之前版本存在安全漏洞，该漏洞源于未限制远程帖子投票选项的最大数量，可能导致资源消耗过大和拒绝服务。

CVSS 7.5 · High EPSS 0.55% · P44

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking
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I. Basic Information for CVE-2026-23962

Vulnerability Information
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Vulnerability Title
Mastodon vulnerable to Denial of Service from a single post (client/server)
Source: CVE Program / CVE List V5
Vulnerability Description
Mastodon is a free, open-source social network server based on ActivityPub. Mastodon versions before v4.3.18, v4.4.12, and v4.5.5 do not have a limit on the maximum number of poll options for remote posts, allowing attackers to create polls with a very large amount of options, greatly increasing resource consumption. Depending on the number of poll options, an attacker can cause disproportionate resource usage in both Mastodon servers and clients, potentially causing Denial of Service either server-side or client-side. 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:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不加限制或调节的资源分配
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 v4.3.18之前版本、v4.4.12之前版本和v4.5.5之前版本存在安全漏洞，该漏洞源于未限制远程帖子投票选项的最大数量，可能导致资源消耗过大和拒绝服务。
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-2026-23962

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III. Intelligence Information for CVE-2026-23962

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

CVE-2026-23964 6.5 MEDIUM Mastodon has insufficient access control to push notification settings
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-770

V. Comments for CVE-2026-23962

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