Unsanitized events sent over Websocket to regular users in a High Availability environment

published 2023-03-31 3 y ago modified 2026-06-17 4 mo ago also BIT-mattermost-2023-1775 , EUVD-2023-0949 , GHSA-8jhh-3jf2-pfwr

cvss: 4.3; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.5%; EPSS 0.5% chance of exploitation in 30 days, percentile 46%
public exploits: 0; none known

When running in a High Availability configuration, Mattermost fails to sanitize some of the user_updated and post_deleted events broadcast to all users, leading to disclosure of sensitive information to some of the users with currently connected Websocket clients.

Patch / fix

fixed in 5

go github.com/mattermost/mattermost-server 7.1.6, 7.7.2
go github.com/mattermost/mattermost-server/v5 7.1.6
go github.com/mattermost/mattermost-server/v6 7.1.6
bitnami mattermost 7.1.6
Mattermost Mattermost 7.1.6, 7.7.2, 7.8.0

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 23 mo ago (2024-12-06)

Exploit prediction

0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	4.3	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
GitHub	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
NVD	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
OSV	3.1	6.5	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
go	github.com/mattermost/mattermost-server	>=3.3.0, <7.1.6 >=7.7.0, <7.7.2 >=7.1.0, <7.1.6	7.1.6 7.7.2
go	github.com/mattermost/mattermost-server/v5	>=5.0.0, <7.1.6	7.1.6
go	github.com/mattermost/mattermost-server/v6	>=6.0.0, <7.1.6	7.1.6
bitnami	mattermost	<7.1.6 >=7.7.1, <=7.7.1	7.1.6

Affected products

Mattermost Mattermost

Classification

Weakness

CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
CWE-668 Exposure of Resource to Wrong Sphere

References

mattermost.com /security-updates/
vendor-advisory, web
nvd.nist.gov /vuln/detail/CVE-2023-1775
advisory, web
github.com.mattermost /mattermost-server
package
mattermost.com /security-updates
web

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