CVE-2026-47389Network attack vector

Unauthenticated SSRF via IPv4-mapped IPv6 address misclassification

Published Jun 24, 2026 · Updated Jun 24, 2026

SSRF in Mastodon 4.5.0-beta.1 through 4.5.9 allows remote attackers to reach private HTTP services through crafted DNS responses. PrivateAddressCheck.private_address? misclassifies some IPv4-mapped IPv6 addresses as public under Ruby before 3.4, permitting outbound connections to their embedded IPv4 addresses. Exploitation requires control of a domain's DNS and an outbound Mastodon fetch; exposed resources can include loopback services, private networks, and cloud metadata.

CVSS severity8.6
High
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

SSRF in Mastodon 4.5.0-beta.1 through 4.5.9 allows remote attackers to reach private HTTP services through crafted DNS responses. PrivateAddressCheck.private_address? misclassifies some IPv4-mapped IPv6 addresses as public under Ruby before 3.4, permitting outbound connections to their embedded IPv4 addresses. Exploitation requires control of a domain's DNS and an outbound Mastodon fetch; exposed resources can include loopback services, private networks, and cloud metadata.

The record

CVE
CVE-2026-47389
Published
Jun 24, 2026
Updated
Jun 24, 2026
Vendor
Mastodon
Product
Mastodon
Classifications
CWE-184, CWE-918, CWE-200, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 24, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.5.0-beta.1, < 4.5.10

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mastodon · Mastodonversion=>= 4.5.0-beta.1, < 4.5.10

Published CVSS scores

8.6GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-184Incomplete List of Disallowed Inputs
CWE-918Server-Side Request Forgery (SSRF)
CWE-200Exposure of Sensitive Information to an Unauthorized Actor
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo