Mattermost Server vulnerable to user account takeover when Single Sign-On OAuth2 is used

Also known as GHSA-fpcr-4rr5-hpcp, GO-2026-4477

Published 6 y ago 2020-06-19 · modified 4 mo ago 2026-06-17 · JSON

CVSS

8.1

v3.1 · NVD

CISA KEV

not known exploited

EPSS

0.8%

percentile 56%

Public exploits

none known

An issue was discovered in Mattermost Server before 4.0.0, 3.10.2, and 3.9.2, when Single Sign-On OAuth2 is used. An attacker could claim somebody else's account.

Exploit prediction (EPSS)

0.79% probability of exploitation in the next 30 days, higher than 56% of all scored CVEs.

CVSS scores

Assigned by	Version	Score	Vector
NVD	3.1	8.1	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`
NVD	2.0	4.9	`AV:N/AC:M/Au:S/C:P/I:P/A:N`
GitHub	3.1	8.1	`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`

Affected packages

Ecosystem	Package	Affected	Fixed in
go	`github.com/mattermost/mattermost-server`	<3.9.2-0.20170714134023-b17fca0d5ee7 >=3.10.0, <3.10.2 >=3.10.0+incompatible, <3.10.2+incompatible	3.9.2-0.20170714134023-b17fca0d5ee7 3.10.2 3.10.2+incompatible

Classification

Weakness

CWE-287 Improper Authentication
CWE-613 DEPRECATED: Insufficient Session Expiration

References

mattermost.com /security-updates/ · x_refsource_CONFIRM, x_transferred
nvd.nist.gov /vuln/detail/CVE-2017-18906 · advisory
github.com /mattermost/mattermost/commit/259ad46f30d0fac2f7c5c14f3b76b2170f7e90c7 · web
github.com /mattermost/mattermost/commit/b17fca0d5ee7557e3df1cf1d1da8bd749859e35f · web
github.com /mattermost/mattermost/commit/fbc170733e86f09b46ba754dd03304733d2f482f · web
github.com /mattermost/mattermost · package
mattermost.com /security-updates · web
github.com /advisories/GHSA-fpcr-4rr5-hpcp · advisory

Sources

CVE List: CVE-2017-18906
GitHub Advisory: GHSA-fpcr-4rr5-hpcp
NVD: CVE-2017-18906
OSV: GO-2026-4477

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