Mattermost up to 10.11.12/11.3.2/11.4.2/11.5.0 toctou

CVSS Meta Temp Score
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CTI Interest Score
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6.8$0-$5k0.34

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). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Type

Name

Version

License

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

AVACAuCIA
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💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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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

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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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: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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