Is CVE-2026-41259 in the CISA KEV catalog?

No. CVE-2026-41259 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-41259?

CVE-2026-41259 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2026-41259?

CVE-2026-41259 has an EPSS score of 0.21% (12th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-41259?

Upgrade mastodon to 4.5.9 or later.

CVE & CISA-KEV Catalog

CVE-2026-41259

HIGH

7.5

CVSS v3

NVD

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.

CWE-841

How to fix

Remediation Available

mastodonNVD

Affected:>= 4.5.0, < 4.5.9Fixed in:4.5.9CVE-2026-41259derived from NVD

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityHigh

AvailabilityNone

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Exploit Intelligence

0.21%probability of exploitation in 30 days

12thpercentile

Low risk: more likely to be exploited than 12% of all known CVEs.

References

Vendor Advisory1

github.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-28.