CVE-2026-47389
Mastodon SSRF via IPv4-mapped IPv6 DNS records could reach internal endpoints.
Is CVE-2026-47389 being exploited?
Not confirmed. CVE-2026-47389 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.39% probability of exploitation in the next 30 days.
How severe is CVE-2026-47389?
CVE-2026-47389 is rated High with a CVSS score of 8.6. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-47389?
Yes. A fix has been recorded for CVE-2026-47389. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-47389 affect?
CVE-2026-47389 affects Mastodon <4.5.10, Mastodon <4.4.17, Mastodon <4.3.23. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-47389?
Upgrade to 4.5.10+ or latest patch
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Outbound HTTP fetch to internal/private endpoints (e.g., 127.0.0.1, 169.254.169.254) triggered by DNS-controlled domains.
Patch immediately
- affected>= 4.5.0-beta.1 and < 4.5.10
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.