CVE-2026-23963

4.3 MEDIUM
Published: January 22, 2026 Modified: February 02, 2026
View on NVD

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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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://github.com/mastodon/mastodon/releases/tag/v4.3.18
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.4.12
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/releases/tag/v4.5.5
Source: security-advisories@github.com
Release Notes
https://github.com/mastodon/mastodon/security/advisories/GHSA-6x3w-9g92-gvf3
Source: security-advisories@github.com
Vendor Advisory

4 reference(s) from NVD

Quick Stats

CVSS v3 Score
4.3 / 10.0
EPSS (Exploit Probability)
0.1%
17th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

joinmastodon