What is CVE-2023-42451?

CVE-2023-42451 is a high-severity vulnerability in Joinmastodon Mastodon, classified under Use of Incorrectly-Resolved Name or Reference. CVSS score: 7.4/10. Published 2023-09-19.

How severe is CVE-2023-42451?

High severity. CVSS v3 base score is 7.4 out of 10.

Vulnerability in Joinmastodon Mastodon

CVE-2023-42451

Mastodon is a free, open-source social network server based on ActivityPub. Prior to versions 3.5.14, 4.0.10, 4.1.8, and 4.2.0-rc2, under certain circumstances, attackers can exploit a flaw in domain name normalization to spoof domains they do not own. Versions 3.5.14, 4.0.10, 4.1.8, and 4.2.0-rc2 contain a patch for this issue.

Published 2023-09-19 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.007 (50.9th percentile), scored 2026-10-20.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 51st percentile — 50.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Joinmastodon Mastodon — versions 4.2.0
Mastodon — versions < 3.5.14, >= 4.0.0, < 4.0.10, >= 4.1.0, < 4.1.8

Weakness classification (CWE)

CWE-706 — Use of Incorrectly-Resolved Name or Reference

References

github.com/mastodon/mastodon/security/advisories/GHSA-v3xf-c9qf-j667 (Vendor Advisory)
github.com/mastodon/mastodon/commit/eeab3560fc0516070b3fb97e089b15ecab1938c8 (Patch)

Frequently asked questions

What is CVE-2023-42451?: CVE-2023-42451 is a high-severity vulnerability in Joinmastodon Mastodon, classified under Use of Incorrectly-Resolved Name or Reference. CVSS score: 7.4/10. Published 2023-09-19.
How severe is CVE-2023-42451?: High severity. CVSS v3 base score is 7.4 out of 10.