What is CVE-2026-41259?

CVE-2026-41259 is a high-severity vulnerability in Joinmastodon Mastodon, classified under Improper Enforcement of Behavioral Workflow. CVSS score: 7.5/10. Published 2026-04-23.

How severe is CVE-2026-41259?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Joinmastodon Mastodon

CVE-2026-41259

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…

EPSS: 0.001 (17.8th percentile) — read the EPSS interpretation.

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:H/A:N.

Affected products

Joinmastodon Mastodon
Mastodon — versions < 4.3.22, >= 4.4.0-beta.1, < 4.4.16, >= 4.5.0-beta.1, < 4.5.9

Weakness classification (CWE)

CWE-841 — Improper Enforcement of Behavioral Workflow

References

https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh (x_refsource_CONFIRM, Vendor Advisory)

Frequently asked questions

What is CVE-2026-41259?: CVE-2026-41259 is a high-severity vulnerability in Joinmastodon Mastodon, classified under Improper Enforcement of Behavioral Workflow. CVSS score: 7.5/10. Published 2026-04-23.
How severe is CVE-2026-41259?: High severity. CVSS v3 base score is 7.5 out of 10.