Mattermost Server exposes sensitive user status information via REST API version 4 endpoint

published 2020-06-19 6y ago modified 2026-06-17 4mo ago also GHSA-h742-xx59-r9pq , GO-2026-4295 , EUVD-2017-9985

cvss: 5.3; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 60%
public exploits: 0; none known

An issue was discovered in Mattermost Server before 4.2.0, 4.1.1, and 4.0.5. It allows attackers to obtain sensitive information (user statuses) via a REST API version 4 endpoint.

Patch / fix

fixed in 2 distros 2 links 3

go github.com/mattermost/mattermost-server 4.0.5, 4.0.5+incompatible, 4.1.1, 4.1.1+incompatible, 4.2.0, 4.2.0+incompatible
mattermost mattermost_server 4.0.5, 4.1.1

suse opensuse

govulncheck-vulndb openSUSE Leap 15.6 0.0.20260114T191543-150000.1.137.1

suse advisories SUSE-SU-2026:0142-1

govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1

opensuse advisories openSUSE-SU-2026:21483-1

github.com/mattermost/mattermost@3c34e2b commit
github.com/mattermost/mattermost@722fb19 commit
github.com/mattermost/mattermost@d383289 commit

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Exploit prediction

0.93% chance of exploitation in the next 30 days, higher than 60% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:P/I:N/A:N
GitHub	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
go	github.com/mattermost/mattermost-server	<4.0.5 >=4.1.0, <4.1.1 >=4.2.0-rc1, <4.2.0 <4.0.5+incompatible >=4.1.0+incompatible, <4.1.1+incompatible >=4.2.0-rc1+incompatible, <4.2.0+incompatible	4.0.5 4.1.1 4.2.0 4.0.5+incompatible 4.1.1+incompatible 4.2.0+incompatible

Classification

Weakness

CWE-200 Exposure of Sensitive Information to an Unauthorized Actor

References

Sources

Fencer Intel 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.