CyberSecBulletin
CVE-2026-6961NVD status: Analyzed

Mattermost: Improper Limitation of a Pathname to a Restricted Directory

Published Updated By the CyberSecBulletin desk

CVE-2026-6961 is a high-severity improper limitation of a pathname to a restricted directory vulnerability in Mattermost, with a CVSS 3.1 base score of 7.6 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. Affected Mattermost versions: 11.6.0 through 11.6.1; 11.5.0 through 11.5.4; 10.11.0 through 10.11.15, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.3% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Mattermost Server to 10.11.17 or 11.5.5 or 11.6.2, whichever matches your release line, or a later version.
  2. Read the advisory on mattermost.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
MattermostMattermost11.6.0 through 11.6.1; 11.5.0 through 11.5.4; 10.11.0 through 10.11.15; 10.11.0 through 10.11.16Not stated
MattermostMattermost Server10.11.0 up to, but not including, 10.11.17; 11.5.0 up to, but not including, 11.5.5; 11.6.0 up to, but not including, 11.6.210.11.17, 11.5.5, 11.6.2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
HighAdministrator-level access is required first.
User interaction
NoneNo action by a victim is required.
Scope
ChangedThe attack can reach beyond the vulnerable component into other systems.
Confidentiality
NoneNo data is disclosed.
Integrity
HighData or code can be modified at will.
Availability
LowPerformance or availability is reduced.

Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:N/I:H/A:L. Scored by CNA (mattermost.com).

Official description

Mattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 Mattermost fails to sanitize FileInfo.Name received from federated peers during shared channel file sync, which allows an attacker who controls a federated server to write files to arbitrary locations within the target server's filestore via path traversal sequences in the filename field.. Mattermost Advisory ID: MMSA-2026-00661

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Limitation of a Pathname to a Restricted Directory

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

How developers prevent this class of flaw

  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
  • Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

More Improper Limitation of a Pathname to a Restricted Directory vulnerabilities (CWE-22)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in Mattermost

All Mattermost vulnerabilities

Recent Improper Limitation of a Pathname to a Restricted Directory vulnerabilities

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