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CVE-2026-23963
Good to know:
Date: January 21, 2026
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.
Severity Score
Related Resources (6)
Severity Score
Weakness Type (CWE)
Allocation of Resources Without Limits or Throttling
CWE-770Top Fix
Upgrade Version
Upgrade to version https://github.com/mastodon/mastodon.git - v4.5.5;https://github.com/mastodon/mastodon.git - v4.4.12;https://github.com/mastodon/mastodon.git - v4.3.18
CVSS v3.1
| Base Score: |
|
|---|---|
| Attack Vector (AV): | NETWORK |
| Attack Complexity (AC): | LOW |
| Privileges Required (PR): | LOW |
| User Interaction (UI): | NONE |
| Scope (S): | UNCHANGED |
| Confidentiality (C): | NONE |
| Integrity (I): | NONE |
| Availability (A): | LOW |