Resource Abuse Vulnerability in Mastodon Social Network Server
CVE-2026-23963

4.3MEDIUM

Key Information:

Vendor

Mastodon

Status
Mastodon
Vendor
CVE Published:
22 January 2026

What is CVE-2026-23963?

Mastodon, an open-source social network server, prior to versions 4.5.5, 4.4.12, and 4.3.18, was susceptible to a resource abuse vulnerability. This flaw allowed users to set excessively long strings for list names, filter keywords, or both, resulting in significant storage and processing resource usage. A local user could exploit this weakness to hinder their own web interface, either deliberately or via a malicious API client with unwitting approval.

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Affected Version(s)

mastodon < 4.3.18 < 4.3.18

mastodon >= 4.4.0, < 4.4.12 < 4.4.0, 4.4.12

mastodon >= 4.5.0, < 4.5.5 < 4.5.0, 4.5.5

References

https://github.com/mastodon/mastodon/security/advisories/...
x_refsource_CONFIRM
https://github.com/mastodon/mastodon/releases/tag/v4.3.18
x_refsource_MISC
https://github.com/mastodon/mastodon/releases/tag/v4.4.12
x_refsource_MISC

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

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