How severe is CVE-2023-42451?

CVE-2023-42451 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2023-42451 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-42451?

CVE-2023-42451 primarily affects Joinmastodon Mastodon. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-42451?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2023-42451 published?

CVE-2023-42451 was published on 2023-09-19 and last updated on 2026-06-17.

CVE-2023-42451

CVE-2023-42451 is a high-severity vulnerability in Joinmastodon Mastodon with a CVSS 3.x base score of 7.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-706.

Key facts

Severity: High (CVSS 3.x base score 7.4)
EPSS exploit prediction: 1% (43rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-706
Affected product: Joinmastodon Mastodon
Published: 2023-09-19
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2023-42451?: CVE-2023-42451 has a CVSS 3.x base score of 7.4, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2023-42451 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (43rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-42451?: CVE-2023-42451 primarily affects Joinmastodon Mastodon. In total, 5 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-42451?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2023-42451 published?: CVE-2023-42451 was published on 2023-09-19 and last updated on 2026-06-17.

References

Affected products (5)

cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*
cpe:2.3:a:joinmastodon:mastodon:4.2.0:beta1:*:*:*:*:*:*
cpe:2.3:a:joinmastodon:mastodon:4.2.0:beta2:*:*:*:*:*:*
cpe:2.3:a:joinmastodon:mastodon:4.2.0:beta3:*:*:*:*:*:*
cpe:2.3:a:joinmastodon:mastodon:4.2.0:rc1:*:*:*:*:*:*

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