Mattermost Server does not prevent System Admin from arbitrary file creation

published 2020-06-19 6 y ago modified 2026-06-17 4 mo ago also GHSA-9rr5-q43r-ccv4 , GO-2025-4186 , EUVD-2017-9965

cvss: 4.9; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.7%; EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits: 0; none known

An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2 when local storage for files is used. A System Admin can create arbitrary files.

Patch / fix

fixed in 2 distros 2 links 3

go github.com/mattermost/mattermost-server 4.1.2-0.20171004201910-6be8113eb60c, 4.2.1-0.20171004194140-6d3cb2ce07fc, 4.3.0, 4.3.0+incompatible
mattermost mattermost_server 4.1.2, 4.2.1

suse opensuse

govulncheck-vulndb SLE Module for Package Hub 15 SP6, openSUSE Leap 15.6 0.0.20251209T172047-150000.1.127.1

suse advisories SUSE-SU-2025:4395-1

govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

github.com/mattermost/mattermost@6be8113 commit
github.com/mattermost/mattermost@6d3cb2c commit
github.com/mattermost/mattermost@fadd951 commit

Exploit prediction

0.73% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.1	4.9	CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N
NVD	2.0	4.0	AV:N/AC:L/Au:S/C:N/I:P/A:N

Affected packages

ecosystem	package	affected	fixed in
go	github.com/mattermost/mattermost-server	<4.1.2-0.20171004201910-6be8113eb60c >=4.2.0-rc1.0.20171004154238-fadd9514f6e7, <4.2.1-0.20171004194140-6d3cb2ce07fc >=4.3.0-rc1, <4.3.0 >=4.3.0-rc1+incompatible, <4.3.0+incompatible	4.1.2-0.20171004201910-6be8113eb60c 4.2.1-0.20171004194140-6d3cb2ce07fc 4.3.0 4.3.0+incompatible

Classification

Weakness

CWE-732 Incorrect Permission Assignment for Critical Resource
CWE-22 Improper Limitation of a Pathname to a Restricted Directory

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary