Mattermost up to 10.11.19/11.6.4/11.7.2 Shared Channel Inbound Sync improper synchronization

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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6.0$0-$5k1.56+

Summaryinfo

A vulnerability classified as critical has been found in Mattermost up to 10.11.19/11.6.4/11.7.2. This affects an unknown part of the component Shared Channel Inbound Sync Handler. This manipulation causes improper synchronization. The identification of this vulnerability is CVE-2026-10103. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability classified as critical was found in Mattermost up to 10.11.19/11.6.4/11.7.2. Affected by this vulnerability is some unknown processing of the component Shared Channel Inbound Sync Handler. The manipulation with an unknown input leads to a improper synchronization vulnerability. The CWE definition for the vulnerability is CWE-662. The product utilizes multiple threads or processes to allow temporary access to a shared resource that can only be exclusive to one process at a time, but it does not properly synchronize these actions, which might cause simultaneous accesses of this resource by multiple threads or processes. As an impact it is known to affect 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 verify post ownership in the shared channel inbound sync handler, which allows an authenticated remote cluster to modify or delete posts authored by local users or other remotes via crafted sync messages referencing arbitrary post IDs in channels shared with that remote.. Mattermost Advisory ID: MMSA-2026-00689

The advisory is shared at mattermost.com. This vulnerability is known as CVE-2026-10103 since 05/29/2026. The exploitation appears to be easy. The attack can be launched remotely. Neither technical details nor an exploit are publicly available.

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

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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

Exploitinginfo

Class: Improper synchronization
CWE: CWE-662
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: no mitigation known
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.11.20/11.6.5/11.7.3/11.8.0

Timelineinfo

05/29/2026 CVE reserved
07/13/2026 +45 days Advisory disclosed
07/13/2026 +0 days VulDB entry created
07/13/2026 +0 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Status: Confirmed

CVE: CVE-2026-10103 (🔒)
GCVE (CVE): GCVE-0-2026-10103
GCVE (VulDB): GCVE-100-377929

Entryinfo

Created: 07/13/2026 11:07
Changes: 07/13/2026 11:07 (53)
Complete: 🔍
Cache ID: 216::103

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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