What is CVE-2026-47389?

CVE-2026-47389 is a high-severity vulnerability in Mastodon, classified under Incomplete List of Disallowed Inputs. CVSS score: 8.6/10. Published 2026-06-24.

How severe is CVE-2026-47389?

High severity. CVSS v3 base score is 8.6 out of 10.

SSRF in Mastodon

CVE-2026-47389

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, when using Ruby versions older than 3.4, PrivateAddressCheck.private_address? returns false for IPv4-mapped IPv6 addresses (…

CVSS v3 metric

CVSS v3 base score 8.6 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N.

Affected products

Mastodon — versions >= 4.5.0-beta.1, < 4.5.10

Weakness classification (CWE)

CWE-184 — Incomplete List of Disallowed Inputs
CWE-200 — Information Disclosure
CWE-918 — Server-Side Request Forgery (SSRF)

References

security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-47389?: CVE-2026-47389 is a high-severity vulnerability in Mastodon, classified under Incomplete List of Disallowed Inputs. CVSS score: 8.6/10. Published 2026-06-24.
How severe is CVE-2026-47389?: High severity. CVSS v3 base score is 8.6 out of 10.