CVE-2026-23961Network attack vector

Remote suspension bypass via federated post processing

Published Jan 22, 2026 · Updated Jan 22, 2026

Incorrect authorization in Mastodon before 4.3.18, 4.4.0 through 4.4.11, and 4.5.0 through 4.5.4 allows remote attackers to bypass suspension. Timeline and ActivityPub-processing logic fails to reject boosted known posts and, in affected release branches, new posts from suspended remote users. Exploitation requires federated content from a suspended remote account; the bounded impact is unauthorized timeline placement, not data disclosure or service interruption.

CVSS severity5.3
Medium
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in Mastodon before 4.3.18, 4.4.0 through 4.4.11, and 4.5.0 through 4.5.4 allows remote attackers to bypass suspension. Timeline and ActivityPub-processing logic fails to reject boosted known posts and, in affected release branches, new posts from suspended remote users. Exploitation requires federated content from a suspended remote account; the bounded impact is unauthorized timeline placement, not data disclosure or service interruption.

The record

CVE
CVE-2026-23961
Published
Jan 22, 2026
Updated
Jan 22, 2026
Vendor
Mastodon
Product
Mastodon
Classifications
CWE-863, T1565.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 22, 2026CVE publishedPublication date reported by the CVE source.
  2. Jan 22, 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=< 4.3.18
  2. Affected versionversion=>= 4.4.0, < 4.4.12
  3. Affected versionversion=>= 4.5.0, < 4.5.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mastodon · Mastodonversion=< 4.3.18; version=>= 4.4.0, < 4.4.12; version=>= 4.5.0, < 4.5.5

Published CVSS scores

5.3GitHub, Inc.CVSS: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 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-863Incorrect Authorization
T1565.001Stored 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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