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Vulnerability · Published May 18, 2026 · Assigned by Mattermost

CVE-2026-4273Insufficient token rotation validation in remote cluster invite confirmation

Low 3.7

In plain English

A low-severity incorrect authorization in Mattermost from Mattermost. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)3.7Low
Exploit odds (30 days)0.1%top 96.5% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/mattermost/mattermost-server10.11.14+incompatible, 11.5.2+incompatibleGO-2026-5432
Gogithub.com/mattermost/mattermost-server5.3.2-0.20260313190740-742e0be95074GHSA-hqpj-f3jh-29vx
Gogithub.com/mattermost/mattermost-server/v5no fix listedGO-2026-5432
Gogithub.com/mattermost/mattermost-server/v6no fix listedGO-2026-5432
Gogithub.com/mattermost/mattermost/server/v88.0.0-20260313190740-742e0be95074GO-2026-5432
Gogithub.com/mattermost/mattermost/server/v810.11.14GHSA-hqpj-f3jh-29vx
Gogithub.com/mattermost/mattermost/server/v88.0.0-20260313190740-742e0be95074GHSA-hqpj-f3jh-29vx
Gogithub.com/mattermost/mattermost/server/v811.5.2GHSA-hqpj-f3jh-29vx

Affected products (as reported)

VendorProductVersions
Mattermost Mattermost 11.5.0 – through 11.5.110.11.0 – through 10.11.13

Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

References