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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-4273

21
FAUCET Score

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate that the RefreshedToken differs from the original invite token during remote cluster invite confirmation which allows an authenticated attacker to bypass token rotation and reuse the original invite token via sending a crafted invite confirmation with a RefreshedToken matching the original token. Mattermost Advisory ID: MMSA-2026-00575

First published: May 18, 2026Last modified: May 18, 2026

Impacted Technologies

VendorProductVersion(s)CPE
>= 10.11.0, < 10.11.14CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
>= 11.5.0, < 11.5.2CPE matchmatch criteria
cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*
>= 10.11.0, <= 10.11.13CPE match
cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:*
>= 11.5.0, <= 11.5.1CPE match
cpe:2.3:a:mattermost:mattermost:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

3.7LOW

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.2
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.14%
Probability of exploitation in next 30 days
EPSS Percentile
3.9%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0014 is in the 0th percentile among its peer group of 21,974 CVEs.

Social Chatter

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

Media Mentions

No media coverage found for this CVE.

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

Remediation

Patch Available

Vendor Patches (4)

gopatch availablevia ghsa
Product: github.com/mattermost/mattermost/server/v8Fixed in: 11.5.2
gopatch availablevia ghsa
Product: github.com/mattermost/mattermost/server/v8Fixed in: 10.11.14
gopatch availablevia ghsa
Product: github.com/mattermost/mattermost/server/v8Fixed in: 8.0.0-20260313190740-742e0be95074
gopatch availablevia ghsa
Product: github.com/mattermost/mattermost-serverFixed in: 5.3.2-0.20260313190740-742e0be95074

Vendor Advisories (1)

goGHSA-hqpj-f3jh-29vxlow

Mattermost doesn't validate that the RefreshedToken differs from the original invite token during remote cluster invite confirmation

May 18, 2026

References

mattermost.com / security-updates
Vendor Advisory