CVE-2026-3590 | Mattermost up to 10.11.12/11.3.2/11.4.2/11.5.0 toctou (EUVD-2026-22915)

VDB-357698 · CVE-2026-3590 · EUVD-2026-22915 MATTERMOST UP TO 10.11.12/11.3.2/11.4.2/11.5.0 TOCTOU HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 6.8 $0-$5k 2.66 Summaryinfo A vulnerability described as critical has been identified in Mattermost up to 10.11.12/11.3.2/11.4.2/11.5.0. Affected by this vulnerability is an unknown functionality. Such manipulation leads to toctou. This vulnerability is listed as CVE-2026-3590. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is recommended. Detailsinfo A vulnerability, which was classified as critical, has been found in Mattermost up to 10.11.12/11.3.2/11.4.2/11.5.0. Affected by this issue is an unknown code block. The manipulation with an unknown input leads to a toctou vulnerability. Using CWE to declare the problem leads to CWE-367. The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the product to perform invalid actions when the resource is in an unexpected state. Impacted is confidentiality, integrity, and availability. CVE summarizes: Mattermost versions 10.11.x <= 10.11.12, 11.5.x <= 11.5.0, 11.4.x <= 11.4.2, 11.3.x <= 11.3.2 fail to enforce atomic single-use consumption of guest magic link tokens, which allows an attacker with access to a valid magic link to establish multiple independent authenticated sessions via concurrent requests.. Mattermost Advisory ID: MMSA-2026-00624 The weakness was presented by Edgar Bellot Micó. The advisory is available at mattermost.com. This vulnerability is handled as CVE-2026-3590 since 03/05/2026. 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 10.11.13, 11.3.3, 11.4.3, 11.5.1 or 11.6.0 eliminates this vulnerability. The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-22915). Productinfo Type Groupware Software Name Mattermost Version 10.11.0 10.11.1 10.11.2 10.11.3 10.11.4 10.11.5 10.11.6 10.11.7 10.11.8 10.11.9 10.11.10 10.11.11 10.11.12 11.0 11.1 11.2 11.3 11.3.0 11.3.1 11.3.2 11.4 11.4.0 11.4.1 11.4.2 11.5.0 License open-source CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv3info VulDB Meta Base Score: 6.9 VulDB Meta Temp Score: 6.8 VulDB Base Score: 7.3 VulDB Temp Score: 7.0 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 6.5 CNA Vector (Mattermost): 🔒 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: Toctou CWE: CWE-367 / CWE-362 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: Mattermost 10.11.13/11.3.3/11.4.3/11.5.1/11.6.0 Timelineinfo 03/05/2026 CVE reserved 04/15/2026 +40 days Advisory disclosed 04/15/2026 +0 days VulDB entry created 04/15/2026 +0 days VulDB entry last update Sourcesinfo Advisory: mattermost.com Researcher: Edgar Bellot Micó Status: Confirmed CVE: CVE-2026-3590 (🔒) GCVE (CVE): GCVE-0-2026-3590 GCVE (VulDB): GCVE-100-357698 EUVD: 🔒 Entryinfo Created: 04/15/2026 13:58 Updated: 04/15/2026 14:17 Changes: 04/15/2026 13:58 (63), 04/15/2026 14:17 (1) Complete: 🔍 Cache ID: 99:B70:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸