Mattermost up to 10.11.13/11.5.1 OAuth Authorization authentication bypass

CVSS Meta Temp Score
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CTI Interest Score
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3.6$0-$5k0.00

Summaryinfo

A vulnerability described as problematic has been identified in Mattermost up to 10.11.13/11.5.1. Impacted is an unknown function of the component OAuth Authorization. The manipulation results in authentication bypass. This vulnerability is identified as CVE-2026-6334. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability classified as problematic has been found in Mattermost up to 10.11.13/11.5.1. Affected is an unknown code block of the component OAuth Authorization. The manipulation with an unknown input leads to a authentication bypass vulnerability. CWE is classifying the issue as CWE-305. The authentication algorithm is sound, but the implemented mechanism can be bypassed as the result of a separate weakness that is primary to the authentication error. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to enforce client identity binding during the OAuth authorization code redemption flow which allows an authenticated OAuth client to redeem authorization codes issued to a different client via a crafted token exchange request.. Mattermost Advisory ID: MMSA-2026-00570

The weakness was released by Dylan Haussermann. The advisory is available at mattermost.com. This vulnerability is traded as CVE-2026-6334 since 04/15/2026. The exploitability is told to be difficult. It is possible to launch the attack remotely. The exploitation needs additional levels of successful authentication. The technical details are unknown and an exploit is not available.

Upgrading to version 10.11.14, 11.5.2 or 11.6.0 eliminates this vulnerability.

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Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 3.7
VulDB Meta Temp Score: 3.6

VulDB Base Score: 4.1
VulDB Temp Score: 3.9
VulDB Vector: 🔒
VulDB Reliability: 🔍

NVD Base Score: 3.8
NVD Vector: 🔒

CNA Base Score: 3.1
CNA Vector (Mattermost): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Authentication bypass
CWE: CWE-305 / CWE-287
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 10.11.14/11.5.2/11.6.0

Timelineinfo

04/15/2026 CVE reserved
05/18/2026 +33 days Advisory disclosed
05/18/2026 +0 days VulDB entry created
06/01/2026 +14 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: Dylan Haussermann
Status: Confirmed

CVE: CVE-2026-6334 (🔒)
GCVE (CVE): GCVE-0-2026-6334
GCVE (VulDB): GCVE-100-364446

Entryinfo

Created: 05/18/2026 10:01
Updated: 06/01/2026 06:59
Changes: 05/18/2026 10:01 (64), 06/01/2026 06:59 (11)
Complete: 🔍
Cache ID: 216::103

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