Predictive Vulnerability Intelligence.

Product

  • Product
  • Pricing
  • Documentation

Company

  • About
  • Partnerships
  • Blog
  • Support

Legal

  • Terms
  • Privacy
  • Data Licensing

© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2018-21263

26
FAUCET Score

CVE-2018-21263 describes an authentication bypass vulnerability in Mattermost Server versions prior to 4.7.0, 4.6.2, and 4.5.2. An attacker could leverage a specially crafted SAML response to authenticate as another user. This vulnerability carries a high severity CVSS score of 8.8, indicating a network-based attack with low privileges required, leading to high impact on confidentiality, integrity, and availability. Despite its severity, there is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 4.5.2CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
>= 4.6.0, < 4.6.2CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
4.7.0CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:4.7.0:rc1:*:*:*:*:*:*
4.7.0CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:4.7.0:rc2:*:*:*:*:*:*
4.7.0CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:4.7.0:rc3:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.8HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.8
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.93%
Probability of exploitation in next 30 days
EPSS Percentile
57.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0093 is in the 52nd percentile among its peer group of 17,844 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.3 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

mattermost.com / security-updates
Vendor Advisory