CVE-2026-2578: Github.com/mattermost/mattermost/server/v8 Mattermost Fails To Preserve The Vulnerability
MODERATECVE-2026-2578 is a MODERATE (CVSS 4.3) mattermost fails to preserve the vulnerability (CWE-201: Insertion of Sensitive Information Into Sent Data) affecting Github.com/mattermost/mattermost/server/v8 libraries in the Go ecosystem. The issue involves mattermost fails to preserve the redacted state of burn-on-read posts during deletion. Remediation is available by upgrading affected packages to version 8.0.0-20260127062706-c6b205f0d770, 5.3.2-0.20260127062706-c6b205f0d770, 10.11.11, 11.2.3, 11.3.1.
CVE-2026-2578 at a Glance
Security Impact
CVSS: 4.3
The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N).
How to Fix CVE-2026-2578
To remediate this vulnerability, upgrade all affected Github.com/mattermost/mattermost/server/v8 dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.
Upgrade github.com/mattermost/mattermost/server/v8 to 8.0.0-20260127062706-c6b205f0d770Upgrade github.com/mattermost/mattermost-server to 5.3.2-0.20260127062706-c6b205f0d770Upgrade github.com/mattermost/mattermost-server to 10.11.11Upgrade github.com/mattermost/mattermost-server to 11.2.3Upgrade github.com/mattermost/mattermost-server to 11.3.1Run the following command in your project directory to verify that all resolved dependencies use the patched release:
inspect dependencies for github.com/mattermost/mattermost/server/v8How to Check if You Are Affected
To determine whether your application is affected by CVE-2026-2578, inspect your project dependencies for Github.com/mattermost/mattermost/server/v8:
inspect dependencies for github.com/mattermost/mattermost/server/v8Analyze the terminal output to locate any version of Github.com/mattermost/mattermost/server/v8 in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 8.0.0-20260127062706-c6b205f0d770), your application is affected.
Note: Verify declared build manifests and deployed runtime container environments.
Technical Details
Vulnerability Mechanism & Technical Analysis
This vulnerability is classified under CWE-201: Insertion of Sensitive Information Into Sent Data, where the code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor. In Github.com/mattermost/mattermost/server/v8, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.
Source Advisory Statement
CVE-2026-2578 Affected Github.com/mattermost/mattermost/server/v8 Versions
5 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
github.com/mattermost/mattermost/server/v8
|
Go |
< 8.0.0-20260127062706-c6b205f0d770
|
8.0.0-20260127062706-c6b205f0d770
|
|
github.com/mattermost/mattermost-server
|
Go |
< 5.3.2-0.20260127062706-c6b205f0d770
|
5.3.2-0.20260127062706-c6b205f0d770
|
|
github.com/mattermost/mattermost-server
|
Go |
≥ 10.11.0-rc1
< 10.11.11
|
10.11.11
|
|
github.com/mattermost/mattermost-server
|
Go |
≥ 11.2.0-rc1
< 11.2.3
|
11.2.3
|
|
github.com/mattermost/mattermost-server
|
Go |
≥ 11.3.0-rc1
< 11.3.1
|
11.3.1
|
References
Frequently Asked Questions
What is CVE-2026-2578?
Which Github.com/mattermost/mattermost/server/v8 versions are affected?
What version fixes CVE-2026-2578?
Is github.com/mattermost/mattermost/server/v8 affected?
Is github.com/mattermost/mattermost-server affected?
What is the CVSS score of CVE-2026-2578?
What CWE is associated with CVE-2026-2578?
How can I check Go dependencies for CVE-2026-2578?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-3rhr-jr63-hwq5",
"modified" : "2026-03-17T20:02:36Z",
"published" : "2026-03-16T15:30:43Z",
"aliases" : [ "CVE-2026-2578" ],
"summary" : "Mattermost fails to preserve the redacted state of burn-on-read posts during deletion",
"details" : "Mattermost versions 11.3.x <= 11.3.0 fail to preserve the redacted state of burn-on-read posts during deletion which allows channel members to access unrevealed burn-on-read message contents via the WebSocket post deletion event. Mattermost Advisory ID: MMSA-2026-00579",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N"
} ],
"affected" : [ {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost/server/v8"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "8.0.0-20260127062706-c6b205f0d770"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "0"
}, {
"fixed" : "5.3.2-0.20260127062706-c6b205f0d770"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "10.11.0-rc1"
}, {
"fixed" : "10.11.11"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.2.0-rc1"
}, {
"fixed" : "11.2.3"
} ]
} ]
}, {
"package" : {
"ecosystem" : "Go",
"name" : "github.com/mattermost/mattermost-server"
},
"ranges" : [ {
"type" : "ECOSYSTEM",
"events" : [ {
"introduced" : "11.3.0-rc1"
}, {
"fixed" : "11.3.1"
} ]
} ]
} ],
"references" : [ {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-2578"
}, {
"type" : "WEB",
"url" : "https://github.com/mattermost/mattermost/commit/c6b205f0d77080ef805783de0628b9526af7faec"
}, {
"type" : "PACKAGE",
"url" : "https://github.com/mattermost/mattermost"
}, {
"type" : "WEB",
"url" : "https://mattermost.com/security-updates"
} ],
"database_specific" : {
"cwe_ids" : [ "CWE-201" ],
"severity" : "MODERATE",
"github_reviewed" : true,
"github_reviewed_at" : "2026-03-17T20:02:36Z",
"nvd_published_at" : "2026-03-16T14:19:30Z"
}
}