CVE-2026-23963
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2026-01-22

Last updated on: 2026-02-02

Assigner: GitHub, Inc.

Description
Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 4.5.5, 4.4.12, and 4.3.18, the server does not enforce a maximum length for the names of lists or filters, or for filter keywords, allowing any user to set an arbitrarily long string as the name or keyword. Any local user can abuse the list or filter fields to cause disproportionate storage and computing resource usage. They can additionally cause their own web interface to be unusable, although they must intentionally do this to themselves or unknowingly approve a malicious API client. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.
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Meta Information
Published
2026-01-22
Last Modified
2026-02-02
Generated
2026-06-16
AI Q&A
2026-01-22
EPSS Evaluated
2026-06-15
NVD
CVE-2026-23963
EUVD
EUVD-2026-4209
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
joinmastodon mastodon to 4.3.18 (exc)
joinmastodon mastodon From 4.4.0 (inc) to 4.4.12 (exc)
joinmastodon mastodon From 4.5.0 (inc) to 4.5.5 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-770 The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.
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Executive Summary

This vulnerability in Mastodon versions prior to v4.3.18, v4.4.12, and v4.5.5 occurs because the server does not enforce maximum length limits on list names, filter names, and filter keywords. This allows any local user to set arbitrarily long strings for these fields, which can lead to excessive consumption of storage and computing resources. Users can also make their own web interface unusable, either intentionally or by unknowingly approving a malicious API client. The issue is due to allocation of resources without limits or throttling. [1]

Impact Analysis

The vulnerability can cause disproportionate usage of storage and computing resources on the Mastodon server, potentially degrading performance. Additionally, a user can render their own web interface unusable. However, it does not impact confidentiality or integrity, and the availability impact is low. [1]

Mitigation Strategies

To mitigate this vulnerability, you should upgrade your Mastodon server to version v4.3.18, v4.4.12, or v4.5.5 or later, as these versions have patched the issue by enforcing maximum length limits on list names, filter names, and filter keywords. [1]

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