CVE-2026-23962 json
Mastodon vulnerable to Denial of Service from a single post (client/server)
published 2026-01-22 9 mo ago modified 2026-09-08 2 mo ago also BIT-mastodon-2026-23962 , EUVD-2026-4208 , GHSA-gg8q-rcg7-p79g
- cvss
- 7.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.5%
- EPSS 0.5% chance of exploitation in 30 days, percentile 46%
- public exploits
- 0
- none known
Summary
Mastodon is a free, open-source social network server based on ActivityPub. Mastodon versions before v4.3.18, v4.4.12, and v4.5.5 do not have a limit on the maximum number of poll options for remote posts, allowing attackers to create polls with a very large amount of options, greatly increasing resource consumption. Depending on the number of poll options, an attacker can cause disproportionate resource usage in both Mastodon servers and clients, potentially causing Denial of Service either server-side or client-side. Mastodon versions v4.5.5, v4.4.12, v4.3.18 are patched.
Patch / fix
- bitnami mastodon 4.3.18, 4.4.12, 4.5.5
- joinmastodon mastodon 4.3.18, 4.4.12, 4.5.5
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 9 mo ago
Exploit prediction
0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| OSV | 3.1 | 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| bitnami | mastodon | <4.3.18 >=4.4.0, <4.4.12 >=4.5.0, <4.5.5 |
4.3.18 4.4.12 4.5.5 |
Affected products
- mastodon mastodon
Classification
- Weakness
-
- CWE-770 Allocation of Resources Without Limits or Throttling
References
-
github.com
/mastodon/mastodon/security/advisories/GHSA-gg8q-rcg7-p79g
vendor-advisory, advisory
-
github.com
/mastodon/mastodon/releases/tag/v4.3.18
release-notes, article
-
github.com
/mastodon/mastodon/releases/tag/v4.4.12
release-notes, article
-
github.com
/mastodon/mastodon/releases/tag/v4.5.5
release-notes, article
-
nvd.nist.gov
/vuln/detail/CVE-2026-23962
web
Sources
- CVE List CVE-2026-23962
- NVD CVE-2026-23962
- OSV BIT-mastodon-2026-23962
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.