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CVE-2026-46349— Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring

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组织的一款去中心化社交网络服务器软件。 Mastodon 4.5.10之前版本、4.4.17之前版本和4.3.23之前版本存在加密问题漏洞，该漏洞源于对具有链式数据签名的传入活动规范化处理不足，可能导致攻击者能够重新排列来自第三方的有效签名JSON-LD活动，使其以不同方式处理。

CVSS 5.3 · Medium EPSS 0.19% · P8

Possible ATT&CK Techniques 1 AI

T1556.007 · Hybrid Identity

Affected Version Matrix 1

VendorProduct Version RangeStatus
mastodon mastodon >= 4.5.0-beta.1, < 4.5.10 affected
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I. Basic Information for CVE-2026-46349

Vulnerability Information
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Vulnerability Title
Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring
Source: CVE Program / CVE List V5
Vulnerability Description
Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, Mastodon's normalization of incoming activities signed with Linked-Data Signatures does not sufficiently protect the activities from a certain class of spoofing, allowing attackers to re-arrange a valid signed JSON-LD activity from a third-party actor to have it processed differently. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.
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
密码学签名的验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
Mastodon 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Mastodon是Mastodon组织的一款去中心化社交网络服务器软件。 Mastodon 4.5.10之前版本、4.4.17之前版本和4.3.23之前版本存在加密问题漏洞，该漏洞源于对具有链式数据签名的传入活动规范化处理不足，可能导致攻击者能够重新排列来自第三方的有效签名JSON-LD活动，使其以不同方式处理。
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 >= 4.5.0-beta.1, < 4.5.10 -

II. Public POCs for CVE-2026-46349

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III. Intelligence Information for CVE-2026-46349

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Vendor Advisories for CVE-2026-46349 (1)

Same Patch Batch · mastodon · 2026-06-24 · 6 CVEs total

CVE-2026-47389 8.6 HIGH Mastodon: SSRF protection bypass on older Ruby versions
CVE-2026-50129 7.5 HIGH Mastodon: Persistent anonymous DoS via unhandled NoMethodError in MATH_TRANSFORMER
CVE-2026-48028 6.5 MEDIUM Mastodon: Removal of integrity-protected JSON entries from signed activities
CVE-2026-50128 5.3 MEDIUM Mastodon: Spoofing of attribution domains
CVE-2026-46348 Mastodon: SSRF Bypass via IPv6 Unspecified Address (::)

IV. Related Vulnerabilities

Same product: mastodon
Same vendor: mastodon
Same weakness: CWE-347

V. Comments for CVE-2026-46349

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