Vulnerability Details CVE-2026-6850
Mattermost versions 11.7.x <= 11.7.2, 11.6.x <= 11.6.4, 10.11.x <= 10.11.19 fail to validate the length and content of message attachment field values, which allows an authenticated attacker to cause a denial of service for all users in a channel via a post containing a specially crafted payload that triggers catastrophic backtracking in the client-side markdown parser.. Mattermost Advisory ID: MMSA-2026-00658
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 14.3%
CVSS Severity
CVSS v3 Score 6.5
References
Products affected by CVE-2026-6850
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cpe:2.3:a:mattermost:mattermost_server:10.11.0
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cpe:2.3:a:mattermost:mattermost_server:10.11.1
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cpe:2.3:a:mattermost:mattermost_server:10.11.10
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cpe:2.3:a:mattermost:mattermost_server:10.11.11
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cpe:2.3:a:mattermost:mattermost_server:10.11.12
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cpe:2.3:a:mattermost:mattermost_server:10.11.13
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cpe:2.3:a:mattermost:mattermost_server:10.11.14
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cpe:2.3:a:mattermost:mattermost_server:10.11.15
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cpe:2.3:a:mattermost:mattermost_server:10.11.16
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cpe:2.3:a:mattermost:mattermost_server:10.11.17
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cpe:2.3:a:mattermost:mattermost_server:10.11.18
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cpe:2.3:a:mattermost:mattermost_server:10.11.19
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cpe:2.3:a:mattermost:mattermost_server:10.11.2
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cpe:2.3:a:mattermost:mattermost_server:10.11.3
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cpe:2.3:a:mattermost:mattermost_server:10.11.4
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cpe:2.3:a:mattermost:mattermost_server:10.11.5
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cpe:2.3:a:mattermost:mattermost_server:10.11.6
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cpe:2.3:a:mattermost:mattermost_server:10.11.7
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cpe:2.3:a:mattermost:mattermost_server:10.11.8
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cpe:2.3:a:mattermost:mattermost_server:10.11.9
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cpe:2.3:a:mattermost:mattermost_server:11.6.0
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cpe:2.3:a:mattermost:mattermost_server:11.6.1
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cpe:2.3:a:mattermost:mattermost_server:11.6.2
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cpe:2.3:a:mattermost:mattermost_server:11.6.3
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cpe:2.3:a:mattermost:mattermost_server:11.6.4
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cpe:2.3:a:mattermost:mattermost_server:11.7.0
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cpe:2.3:a:mattermost:mattermost_server:11.7.1
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cpe:2.3:a:mattermost:mattermost_server:11.7.2