CVE-2026-23963Mastodon is a free, open-source social network server based on ActivityPub.
Updated under an hour ago ()
Does this affect you?
It affects joinmastodon mastodon. Add what you run to find out whether that includes you.
No exploitation reported and no EPSS estimate yet.
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Free account, 1 product
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.
- CVSS
- 6.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- CWE-770
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Analyzed
- Record last updated
- Jun 17, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
joinmastodon mastodon joinmastodon:mastodon | before 4.3.18; from 4.4.0 before 4.4.12; from 4.5.0 before 4.5.5 | NVD |
References
- https://github.com/mastodon/mastodon/releases/tag/v4.3.18release-notes
- https://github.com/mastodon/mastodon/releases/tag/v4.4.12release-notes
- https://github.com/mastodon/mastodon/releases/tag/v4.5.5release-notes
- https://github.com/mastodon/mastodon/security/advisories/GHSA-6x3w-9g92-gvf3vendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.