CVE-2026-50128Network attack vectorHinoki check available

Attribution spoofing via ineffective JSON-LD signature coverage

Published Jun 24, 2026 · Updated Jun 24, 2026

Integrity-check bypass in Mastodon 4.3.0 through 4.4.17 and 4.5.0-beta.1 through 4.5.10 allows remote attackers to forge attribution domains. The attributionDomains JSON-LD definition leaves toot:attributionDomains outside effective Linked Data Signature coverage, so that value can change while a signed Update remains valid. No authentication or user interaction is required, and a remote Mastodon server accepts the forged website attribution for the targeted profile.

CVSS severity5.3
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Integrity-check bypass in Mastodon 4.3.0 through 4.4.17 and 4.5.0-beta.1 through 4.5.10 allows remote attackers to forge attribution domains. The attributionDomains JSON-LD definition leaves toot:attributionDomains outside effective Linked Data Signature coverage, so that value can change while a signed Update remains valid. No authentication or user interaction is required, and a remote Mastodon server accepts the forged website attribution for the targeted profile.

The record

CVE
CVE-2026-50128
Published
Jun 24, 2026
Updated
Jun 24, 2026
Vendor
Mastodon
Product
Mastodon
Classifications
CWE-354, T1565.002
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

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Is a vulnerable build present?

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

  1. Affected versionversion=>= 4.3.0, < 4.4.18
  2. Affected versionversion=>= 4.5.0-beta.1, < 4.5.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mastodon · Mastodonversion=>= 4.3.0, < 4.4.18; version=>= 4.5.0-beta.1, < 4.5.11

Published CVSS scores

5.3GitHub_M CNACVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-354Improper Validation of Integrity Check Value
T1565.002Transmitted Data Manipulation

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

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Your stack

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