CVE-2026-41259

Name: CVE-2026-41259
Creator: NVD / NIST
Published: 2026-04-23T19:17:30.027+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 8.2/10EPSS 0.21%

Last modified Jun 17, 2026

CVE-2026-41259 is a high-severity vulnerability rated 8.2/10 on the CVSS scale. 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. EPSS estimates a 0.21% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

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

CVSS 4.0

8.2/10

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.21%

11.6th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-841

Affected Software

Vendor	Product	Versions
Joinmastodon	Mastodon	< 4.3.22
Joinmastodon	Mastodon	>= 4.4.0, < 4.4.16
Joinmastodon	Mastodon	>= 4.5.0, < 4.5.9

References

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

Timeline

Published: Apr 23, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-41259?

How severe is CVE-2026-41259?

CVE-2026-41259 has a CVSS score of 8.2/10 (HIGH severity). The EPSS model estimates a 0.21% probability of exploitation in the next 30 days.

How do I fix CVE-2026-41259?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-41259?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST