Mattermost up to 10.11.19/11.6.4/11.7.2 OAuth Refresh Token Grant Endpoint privilege escalation

CVSS Meta Temp Score
CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.
Current Exploit Price (≈)
Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.
CTI Interest Score
Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
6.0$0-$5k0.00

Summaryinfo

A vulnerability, which was classified as critical, has been found in Mattermost up to 10.11.19/11.6.4/11.7.2. This issue affects some unknown processing of the component OAuth Refresh Token Grant Endpoint. Performing a manipulation results in Remote Privilege Escalation. This vulnerability is identified as CVE-2026-9571. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability, which was classified as critical, was found in Mattermost up to 10.11.19/11.6.4/11.7.2. This affects an unknown functionality of the component OAuth Refresh Token Grant Endpoint. The manipulation with an unknown input leads to a remote privilege escalation vulnerability. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to invalidate OAuth refresh tokens upon user account deactivation, which allows a deactivated user or an attacker in possession of a valid refresh token to obtain new functional access tokens via the OAuth refresh token grant endpoint.. Mattermost Advisory ID: MMSA-2026-00680

It is possible to read the advisory at mattermost.com. This vulnerability is uniquely identified as CVE-2026-9571 since 05/26/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. The technical details are unknown and an exploit is not publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 327418 (Mattermost Server 10.11.x < 10.11.20 / 11.6.x < 11.6.5 / 11.7.x < 11.7.3 Multiple Vulnerabilities (MMSA-2026-00658, MMSA-2026-00676, MMSA-2026-00680, MMSA-2026-00683, MMSA-2026-00688, MMSA-2026-00689, MMSA-2026-00690)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 10.11.20, 11.6.5, 11.7.3 or 11.8.0 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (327418) and CERT Bund (WID-SEC-2026-1932). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Affected

  • Mattermost Mattermost

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.3
VulDB Meta Temp Score: 6.0

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

CVSSv2info

AVACAuCIA
💳💳💳💳💳💳
💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock
UnlockUnlockUnlockUnlockUnlockUnlock

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

Exploitinginfo

Class: Privilege escalation
CWE: Unknown
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-DayUnlockUnlockUnlockUnlock
TodayUnlockUnlockUnlockUnlock

Nessus ID: 327418
Nessus Name: Mattermost Server 10.11.x < 10.11.20 / 11.6.x < 11.6.5 / 11.7.x < 11.7.3 Multiple Vulnerabilities (MMSA-2026-00658, MMSA-2026-00676, MMSA-2026-00680, MMSA-2026-00683, MMSA-2026-00688, MMSA-2026-00689, MMSA-2026-00690)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.11.20/11.6.5/11.7.3/11.8.0

Timelineinfo

05/26/2026 CVE reserved
07/13/2026 +48 days Advisory disclosed
07/13/2026 +0 days VulDB entry created
07/18/2026 +5 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Status: Confirmed

CVE: CVE-2026-9571 (🔒)
GCVE (CVE): GCVE-0-2026-9571
GCVE (VulDB): GCVE-100-377931
CERT Bund: WID-SEC-2026-1932 - Mattermost: Mehrere Schwachstellen erm&ouml;glichen nicht spezifizierten Angriff

Entryinfo

Created: 07/13/2026 11:12
Updated: 07/18/2026 02:57
Changes: 07/13/2026 11:12 (52), 07/13/2026 21:07 (7), 07/18/2026 02:57 (2)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion

No comments yet. Languages: en.

Please log in to comment.

◂ PreviousOverviewNext ▸

Want to know what is going to be exploited?

We predict KEV entries!