CVE-2026-23963CWE-770

Mastodon missing length limits on list names, filter names, and filter keywords

Medium · published January 22, 2026

CVSS v3.1
4.3
EPSS
0%
Percentile
27.7
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
4.3 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
CVSS v4.0
Not supplied
EPSS
0.00352 · 27.7th percentile
Weakness
CWE-770 · Allocation of Resources Without Limits or Throttling
Published
2026-01-22T01:53Z
EPSS history
Timeline
  • 22 JAN 01:53Z
    Mastodon missing length limits on list names, filter names, and filter keywords
    cvelistv5