Improper Enforcement of Behavioral Workflow in Mastodon - CVE-2026-41259
Published: April 23, 2026
Vulnerability identifier: #VU126999
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-41259
CWE-ID: CWE-841
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Mastodon
Affected software:
Mastodon
Mastodon
Detailed vulnerability description
The vulnerability allows a remote attacker to bypass e-mail domain restrictions for signing up.
The vulnerability exists due to improper enforcement of behavioral workflow in e-mail address validation when processing sign-up requests. A remote attacker can use special characters in an e-mail address to bypass e-mail domain restrictions for signing up.
The issue can affect both blocked domains and allow-listed domains because some mail servers interpret certain characters differently.
How to mitigate CVE-2026-41259
Install security update from vendor's website.