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CVE-2026-48028— Mastodon: Removal of integrity-protected JSON entries from signed activities

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，该漏洞源于对使用Linked-Data Signatures签名的传入活动进行规范化处理时未充分保护活动免受特定伪造攻击，可能导致威胁者从第三方有效签名活动中移除JSON条目。

CVSS 6.5 · Medium EPSS 0.18% · P7

Possible ATT&CK Techniques 1 AI

T1565.003 · Runtime Data Manipulation

Affected Version Matrix 3

VendorProduct Version RangeStatus
mastodon mastodon >= 4.5.0-beta.1, < 4.5.10 affected
>= 4.4.0-beta.1, < 4.4.17 affected
< 4.3.23 affected
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I. Basic Information for CVE-2026-48028

Vulnerability Information
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Vulnerability Title
Mastodon: Removal of integrity-protected JSON entries from signed activities
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 threat actors to remove JSON entries from valid signed activities from a third-party actor. 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:L
Source: CVE Program / CVE List V5
Vulnerability Type
完整性检查值验证不恰当
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，该漏洞源于对使用Linked-Data Signatures签名的传入活动进行规范化处理时未充分保护活动免受特定伪造攻击，可能导致威胁者从第三方有效签名活动中移除JSON条目。
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-2026-48028

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III. Intelligence Information for CVE-2026-48028

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Vendor Advisories for CVE-2026-48028 (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-2026-50128 5.3 MEDIUM Mastodon: Spoofing of attribution domains
CVE-2026-46349 5.3 MEDIUM Mastodon: LD-Signature Bypass via JSON-LD Named-Graph Restructuring
CVE-2026-46348 Mastodon: SSRF Bypass via IPv6 Unspecified Address (::)

IV. Related Vulnerabilities

Same product: mastodon
Same vendor: mastodon
Same weakness: CWE-354

V. Comments for CVE-2026-48028

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