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CVE-2017-18883

27
FAUCET Score

CVE-2017-18883 is a critical vulnerability affecting Mattermost Server versions prior to 4.3.0, 4.2.1, and 4.1.2 when configured as an OAuth 2.0 Service Provider. The flaw, categorized as CWE-331 (Insufficient Entropy), stems from low entropy in authorization data, allowing an unauthenticated attacker to potentially compromise confidentiality and integrity. With a CVSS score of 9.1 (CRITICAL), this network-exploitable vulnerability requires no user interaction and has a high impact on data. While no public exploit code or active exploitation has been observed, and community discussion is minimal, its high severity warrants attention.

Impacted Technologies

VendorProductVersion(s)CPE
< 4.1.2CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
>= 4.2.0, < 4.2.1CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
4.3.0CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:4.3.0:rc1:*:*:*:*:*:*
4.3.0CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:4.3.0:rc2:*:*:*:*:*:*
4.3.0CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:4.3.0:rc3:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.1CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
5.2
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.13%
Probability of exploitation in next 30 days
EPSS Percentile
62.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0112 is in the 48th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

gopatch availablevia ghsa
Product: github.com/mattermost/mattermost-serverFixed in: 4.1.2
gopatch availablevia ghsa
Product: github.com/mattermost/mattermost-serverFixed in: 4.2.1
gopatch availablevia ghsa
Product: github.com/mattermost/mattermost-serverFixed in: 4.3.0

Vendor Advisories (1)

goGHSA-w8cc-3h7q-jhc3medium

Mattermost Server has low entropy for authorization data as an OAuth 2.0 Service Provider

May 24, 2022

References

mattermost.com / security-updates
Vendor Advisory