CVE-2026-23963
Medium · 4.3CVSS
4.3
EPSS
0.4%
Published
Jan 22, 2026
CISA due date
—
The record
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.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Bitnami | mastodon | 0 | 4.3.18 |
Related vulnerabilities
- CVE-2026-25540 Mastodon is a free, open-source social network server based on ActivityPub. Also affects mastodon
- CVE-2026-23964 Mastodon is a free, open-source social network server based on ActivityPub. Also affects mastodon
- CVE-2026-23962 Mastodon is a free, open-source social network server based on ActivityPub. Also affects mastodon
- CVE-2026-23961 Mastodon is a free, open-source social network server based on ActivityPub. Also affects mastodon
- CVE-2025-67500 Mastodon Error Handling Discrepancy Enables Private Status Existence Enumeration Also affects mastodon
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