How severe is CVE-2026-41259?

CVE-2026-41259 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2026-41259 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-41259?

CVE-2026-41259 affects Joinmastodon Mastodon. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-41259?

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.

Does CVE-2026-41259 have an EU (EUVD) identifier?

Yes. CVE-2026-41259 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25282.

When was CVE-2026-41259 published?

CVE-2026-41259 was published on 2026-04-23 and last updated on 2026-06-17.

CVE-2026-41259

CVE-2026-41259 is a high-severity vulnerability in Joinmastodon Mastodon with a CVSS 3.x base score of 7.5. 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-841.

Key facts

Severity: High (CVSS 3.x base score 7.5)
CVSS v4: 8.2
EPSS exploit prediction: 0% (12th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-25282
Weakness: CWE-841
Affected product: Joinmastodon Mastodon
Published: 2026-04-23
Last modified: 2026-06-17

Description

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, but fails to restrict characters that are interpreted differently by some mailing servers. This vulnerability is fixed in v4.5.9, v4.4.16, and v4.3.22.

Frequently asked questions

What is 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, but fails to restrict characters that are interpreted differently by some mailing servers. This vulnerability is fixed in v4.5.9, v4.4.16, and v4.3.22.
How severe is CVE-2026-41259?: CVE-2026-41259 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2026-41259 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (12th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-41259?: CVE-2026-41259 affects Joinmastodon Mastodon. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-41259?: 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.
Does CVE-2026-41259 have an EU (EUVD) identifier?: Yes. CVE-2026-41259 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25282.
When was CVE-2026-41259 published?: CVE-2026-41259 was published on 2026-04-23 and last updated on 2026-06-17.

References

https://github.com/mastodon/mastodon/security/advisories/GHSA-5r37-qpwq-2jhh

Affected products (1)

cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*

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