CVE-2026-41259 | Mastodon up to 4.3.21/4.4.15/4.5.8 Mail Address behavioral workflow (GHSA-5r37-qpwq-2jhh / EUVD-2026-25282)

VDB-359198 · CVE-2026-41259 · GHSA-5R37-QPWQ-2JHH MASTODON UP TO 4.3.21/4.4.15/4.5.8 MAIL ADDRESS BEHAVIORAL WORKFLOW HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 5.1 $0-$5k 1.37+ Summaryinfo A vulnerability classified as problematic was found in Mastodon up to 4.3.21/4.4.15/4.5.8. This issue affects some unknown processing of the component Mail Address Handler. Such manipulation leads to behavioral workflow. This vulnerability is listed as CVE-2026-41259. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised. Detailsinfo A vulnerability was found in Mastodon up to 4.3.21/4.4.15/4.5.8. It has been rated as problematic. Affected by this issue is an unknown function of the component Mail Address Handler. The manipulation with an unknown input leads to a behavioral workflow vulnerability. Using CWE to declare the problem leads to CWE-841. The product supports a session in which more than one behavior must be performed by an actor, but it does not properly ensure that the actor performs the behaviors in the required sequence. Impacted is integrity. CVE summarizes: 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. The advisory is available at github.com. This vulnerability is handled as CVE-2026-41259 since 04/18/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available. Upgrading to version 4.3.22, 4.4.16 or 4.5.9 eliminates this vulnerability. The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-25282). Productinfo Name Mastodon Version 4.3.0 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6 4.3.7 4.3.8 4.3.9 4.3.10 4.3.11 4.3.12 4.3.13 4.3.14 4.3.15 4.3.16 4.3.17 4.3.18 4.3.19 4.3.20 4.3.21 4.4.0 4.4.1 4.4.2 4.4.3 4.4.4 4.4.5 4.4.6 4.4.7 4.4.8 4.4.9 4.4.10 4.4.11 4.4.12 4.4.13 4.4.14 4.4.15 4.5.0 4.5.1 4.5.2 4.5.3 4.5.4 4.5.5 4.5.6 4.5.7 4.5.8 Website Product: https://github.com/mastodon/mastodon/ CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA CVSS-B Score: 🔒 CNA CVSS-BT Score: 🔒 CNA Vector: 🔒 CVSSv3info VulDB Meta Base Score: 5.3 VulDB Meta Temp Score: 5.1 VulDB Base Score: 5.3 VulDB Temp Score: 5.1 VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Behavioral workflow CWE: CWE-841 / CWE-840 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: Mastodon 4.3.22/4.4.16/4.5.9 Timelineinfo 04/18/2026 CVE reserved 04/23/2026 +5 days Advisory disclosed 04/23/2026 +0 days VulDB entry created 04/24/2026 +0 days VulDB entry last update Sourcesinfo Product: github.com Advisory: GHSA-5r37-qpwq-2jhh Status: Confirmed CVE: CVE-2026-41259 (🔒) GCVE (CVE): GCVE-0-2026-41259 GCVE (VulDB): GCVE-100-359198 EUVD: 🔒 Entryinfo Created: 04/23/2026 23:13 Updated: 04/24/2026 00:04 Changes: 04/23/2026 23:13 (66), 04/24/2026 00:04 (1) Complete: 🔍 Cache ID: 99:7A4:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸