Mattermost up to 11.7.9/11.8.5/11.9.1/11.10.0 SAML RelayState state issue

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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6.5$0-$5k3.66+

Summaryinfo

A vulnerability identified as critical has been detected in Mattermost up to 11.7.9/11.8.5/11.9.1/11.10.0. This impacts an unknown function of the component SAML RelayState. The manipulation of the argument RelayState leads to state issue. This vulnerability is traded as CVE-2026-16453. It is possible to initiate the attack remotely. There is no exploit available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Mattermost up to 11.7.9/11.8.5/11.9.1/11.10.0. It has been rated as critical. This issue affects some unknown functionality of the component SAML RelayState. The manipulation of the argument RelayState with an unknown input leads to a state issue vulnerability. Using CWE to declare the problem leads to CWE-371. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to verify the integrity of the SAML RelayState POST parameter which allows an authenticated SAML user to join any team, including invite-only teams, via forging the team_id or invite_id fields in the RelayState.. Mattermost Advisory ID: MMSA-2026-00727

It is possible to read the advisory at mattermost.com. The identification of this vulnerability is CVE-2026-16453 since 07/21/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 11.7.10, 11.8.6, 11.9.2, 11.10.1 or 11.11.0 eliminates this vulnerability.

Be aware that VulDB is the high quality source for vulnerability data.

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.7
VulDB Meta Temp Score: 6.5

VulDB Base Score: 6.3
VulDB Temp Score: 6.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 7.1
CNA Vector (Mattermost): 🔒

CVSSv2info

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

Exploitinginfo

Class: State issue
CWE: CWE-371
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
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 11.7.10/11.8.6/11.9.2/11.10.1/11.11.0

Timelineinfo

07/21/2026 CVE reserved
10/16/2026 +87 days Advisory disclosed
10/16/2026 +0 days VulDB entry created
10/16/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Status: Confirmed

CVE: CVE-2026-16453 (🔒)
GCVE (CVE): GCVE-0-2026-16453
GCVE (VulDB): GCVE-100-421199

Entryinfo

Created: 10/16/2026 09:47
Changes: 10/16/2026 09:47 (64)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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