CVE-2026-6961Network attack vector

Arbitrary file write via federated filename traversal

Published Jun 12, 2026 · Updated Jun 12, 2026

Path traversal in Mattermost Server allows remote attackers controlling a federated peer to write files to arbitrary target filestore locations. During shared-channel file synchronization, the receiving server uses peer-supplied FileInfo.Name values without sanitizing path separators or traversal elements before resolving storage paths. Control of a trusted federated server is required; crafted names can place attacker-supplied files at arbitrary filestore locations without established code execution.

CVSS severity7.6
High
EPSS probability0.30%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Path traversal in Mattermost Server allows remote attackers controlling a federated peer to write files to arbitrary target filestore locations. During shared-channel file synchronization, the receiving server uses peer-supplied FileInfo.Name values without sanitizing path separators or traversal elements before resolving storage paths. Control of a trusted federated server is required; crafted names can place attacker-supplied files at arbitrary filestore locations without established code execution.

The record

CVE
CVE-2026-6961
Published
Jun 12, 2026
Updated
Jun 12, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-22, T1565.001
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Jun 12, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 12, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.11.0 <=10.11.15
  2. Affected versionversion=10.11.0 <=10.11.16
  3. Affected versionversion=11.5.0 <=11.5.4
  4. Affected versionversion=11.6.0 <=11.6.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.15; version=10.11.0 <=10.11.16; version=11.5.0 <=11.5.4; version=11.6.0 <=11.6.1

Published CVSS scores

7.6Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-22Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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