CVE-2026-41259
highMastodon is a free, open-source social network server based on ActivityPub.
Vendor / product: Joinmastodon — mastodon
Mastodon is a free, open-source social network server based on ActivityPub. Prior to v4.5.9, v4.4.16, and v4.3.22, Mastodon allows restricting new user sign-up based on e-mail domain names, and performs basic validation on e-mail addresses, but fails to restrict characters that are interpreted differently by some mailing servers. This vulnerability is fixed in v4.5.9, v4.4.16, and v4.3.22.
CVSS
7.5
7.5 (CVSS v3.1)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Severity source: NVD CVSS v3.1 (nvd@nist.gov)
Timeline (UTC)
Published: 2026-04-23 19:17
Modified: 2026-11-11 23:10
NVD status: Analyzed
Last synced 3 hours ago
Verified against the source API 2026-11-11 23:12 UTC
Exploitation
Not listed in CISA KEV (as of last catalog sync)
Absence from KEV does not mean a CVE is not exploited. Exploitation status: unknown (no authoritative evidence in our sources).
Affected products
joinmastodon / mastodon <4.3.22, ≥4.4.0 <4.4.16, ≥4.5.0 <4.5.9
Weakness classification (CWE)
Source: NVD / CISA. “NVD-CWE-Other” and “NVD-CWE-noinfo” mean NVD could not assign a specific weakness.
Mitigation & advisories
References
- https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh security-advisories@github.com
Data sources
NVD CVE API 2.0 — fetched 2026-11-11 23:12 UTC · record ↗