Resource exhaustion in Joinmastodon Mastodon
CVE-2026-23962
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (44.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: -0.000
Affected products
- Joinmastodon Mastodon
- Mastodon — versions < 4.3.18, >= 4.4.0, < 4.4.12, >= 4.5.0, < 4.5.5
Weakness classification (CWE)
References
- github.com/mastodon/mastodon/security/advisories/GHSA-gg8q-rcg7-p79g (Vendor Advisory)
- github.com/mastodon/mastodon/releases/tag/v4.3.18 (Release Notes)
- github.com/mastodon/mastodon/releases/tag/v4.4.12 (Release Notes)
- github.com/mastodon/mastodon/releases/tag/v4.5.5 (Release Notes)
Frequently asked questions
- What is CVE-2026-23962?
- CVE-2026-23962 is a high-severity vulnerability in Joinmastodon Mastodon, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-01-22.
- How severe is CVE-2026-23962?
- High severity. CVSS v3 base score is 7.5 out of 10.