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CVE-2026-47389— Mastodon: SSRF protection bypass on older Ruby versions

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之前版本存在安全漏洞，该漏洞源于使用Ruby 3.4之前版本时，PrivateAddressCheck.private_address?函数对IPv4映射的IPv6地址验证错误，可能导致控制DNS的攻击者通过发布包含映射地址的AAAA记录，使Mastodon发出的出站HTTP请求建立到内部IPv4地址的TCP连接，包括回环地址和云元数据端点，从而导致服务端请求

CVSS 8.6 · High EPSS 0.39% · P31

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-2026-47389

Vulnerability Information
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Vulnerability Title
Mastodon: SSRF protection bypass on older Ruby versions
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, when using Ruby versions older than 3.4, PrivateAddressCheck.private_address? returns false for IPv4-mapped IPv6 addresses (::ffff:a.b.c.d) corresponding to some private IPv4 addresses, depending on Ruby version, this can include loopback, RFC1918 private networks, and link-local space. An attacker who controls DNS for any domain can publish an AAAA record with such a mapped address; any outbound HTTP fetch Mastodon performs against that hostname then opens a real TCP connection to the underlying IPv4 address, including 127.0.0.1 and cloud-metadata endpoints such as 169.254.169.254. 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:C/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
不完整的黑名单
Source: CVE Program / CVE List V5
Vulnerability Title
Mastodon 输入验证错误漏洞
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之前版本存在安全漏洞，该漏洞源于使用Ruby 3.4之前版本时，PrivateAddressCheck.private_address?函数对IPv4映射的IPv6地址验证错误，可能导致控制DNS的攻击者通过发布包含映射地址的AAAA记录，使Mastodon发出的出站HTTP请求建立到内部IPv4地址的TCP连接，包括回环地址和云元数据端点，从而导致服务端请求
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-2026-47389

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III. Intelligence Information for CVE-2026-47389

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Vendor Advisories for CVE-2026-47389 (1)

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

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-2026-46349 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-184

V. Comments for CVE-2026-47389

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