WebApp crash via improper validation of proto style in attachments

published 2025-01-15 21 mo ago modified 2026-09-10 1 mo ago also GHSA-8j3q-gc9x-7972 , GO-2025-3393 , EUVD-2025-0093

cvss: 6.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.6%; EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits: 0; none known

Mattermost versions 10.2.x <= 10.2.0, 9.11.x <= 9.11.5, 10.0.x <= 10.0.3, 10.1.x <= 10.1.3 fail to properly validate the style of proto supplied to an action's style in post.props.attachments, which allows an attacker to crash the frontend via crafted malicious input.

Patch / fix

fixed in 3 distros 2

go github.com/mattermost/mattermost/server/v8 8.0.0-20241127161322-25ff7a3779a5, 9.11.6, 10.0.4, 10.1.4, 10.2.1
go github.com/mattermost/mattermost-server 9.11.6+incompatible, 10.0.4+incompatible, 10.1.4+incompatible, 10.2.1+incompatible
Mattermost Mattermost 9.11.6, 10.0.4, 10.1.4, 10.2.1, 10.3.0

suse opensuse

govulncheck-vulndb SLE Module for Package Hub 15 SP6, openSUSE Leap 15.6 0.0.20250128T150132-150000.1.29.1

suse advisories SUSE-SU-2025:0297-1

govulncheck-vulndb openSUSE Tumbleweed 0.0.20250117T214834-1.1

opensuse advisories openSUSE-SU-2025:14704-1

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 21 mo ago (2025-01-15)

Exploit prediction

0.58% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

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

Affected packages

ecosystem	package	affected	fixed in
go	github.com/mattermost/mattermost/server/v8	>=10.2.0, <10.2.1 >=10.1.0, <10.1.4 >=10.0.0, <10.0.4 >=9.11.0, <9.11.6 <8.0.0-20241127161322-25ff7a3779a5	10.2.1 10.1.4 10.0.4 9.11.6 8.0.0-20241127161322-25ff7a3779a5
go	github.com/mattermost/mattermost-server	>=9.11.0+incompatible, <9.11.6+incompatible >=10.0.0+incompatible, <10.0.4+incompatible >=10.1.0+incompatible, <10.1.4+incompatible >=10.2.0+incompatible, <10.2.1+incompatible	9.11.6+incompatible 10.0.4+incompatible 10.1.4+incompatible 10.2.1+incompatible
go	github.com/mattermost/mattermost-server/v5	all versions	no fix listed
go	github.com/mattermost/mattermost-server/v6	all versions	no fix listed

Affected products

Mattermost Mattermost

Classification

Weakness

CWE-704 Incorrect Type Conversion or Cast

References

mattermost.com /security-updates
web, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2025-21088
advisory
github.com /mattermost/mattermost
package
pkg.go.dev /vuln/GO-2025-3393
web
github.com /advisories/GHSA-8j3q-gc9x-7972
advisory

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