CVE-2017-18879 json
Mattermost Server is vulnerable to XSS through author_link field in Slack attachments
published 2020-06-19 6 y ago modified 2026-06-17 4 mo ago also GHSA-498j-wxww-j897 , GO-2025-4189 , EUVD-2017-9969
- cvss
- 6.1
- 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 53%
- public exploits
- 0
- none known
Summary
An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2. XSS could occur via the author_link field of a Slack attachment.
Patch / fix
- go github.com/mattermost/mattermost-server 4.1.2, 4.1.2+incompatible, 4.2.1, 4.2.1+incompatible, 4.3.0, 4.3.0+incompatible
- mattermost mattermost_server 4.1.2, 4.2.1
- 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
Exploit prediction
0.69% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| NVD | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
| NVD | 2.0 | 4.3 | AV:N/AC:M/Au:N/C:N/I:P/A:N |
| GitHub | 3.1 | 6.1 | CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-server | <4.1.2 >=4.2.0, <4.2.1 >=4.3.0-rc1, <4.3.0 <4.1.2+incompatible >=4.2.0+incompatible, <4.2.1+incompatible >=4.3.0-rc1+incompatible, <4.3.0+incompatible |
4.1.2 4.2.1 4.3.0 4.1.2+incompatible 4.2.1+incompatible 4.3.0+incompatible |
Classification
- Weakness
-
- CWE-79 Improper Neutralization of Input During Web Page Generation
References
-
mattermost.com
/security-updates/
vendor-advisory
-
nvd.nist.gov
/vuln/detail/CVE-2017-18879
advisory
-
github.com
/mattermost/mattermost
package
-
mattermost.com
/security-updates
web
-
github.com
/advisories/GHSA-498j-wxww-j897
advisory
Sources
- CVE List CVE-2017-18879
- GitHub Advisory GHSA-498j-wxww-j897
- NVD CVE-2017-18879
- OSV GO-2025-4189
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.