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Description
Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to archive the channel before removing persistent notifications which allows authenticated user to crash the server via timing the creation of persistent notification message between the server deleting existing persistent notifications and archiving the channel.. Mattermost Advisory ID: MMSA-2026-00637
Basic information
Type
unreviewed
Severity
medium Advisory on GitHub
Open advisory ↗ Repository advisory
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Source code
Not specified Published (advisory)
2026-05-26 13:30:15 UTC
Updated
2026-05-26 13:30:16 UTC
NVD published
2026-05-22 11:16:22 UTC
EPSS Score
Score
Percentile
0.04%
13.25%
CVSS Scores
Base score
Version
Severity
Vector
5.3
3.1
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CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
CWEs
CWE id
Name
CWE-362
Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
cvelogic
Threat Intelligence