CVE-2026-4273Network attack vector

Authenticated invite-token reuse via unchecked rotation

Published May 18, 2026 · Updated May 18, 2026

Incorrect authorization in Mattermost 10.11.0 through 10.11.13 and 11.5.0 through 11.5.1 allows remote authenticated users to reuse invite tokens. Remote cluster invite confirmation accepts a RefreshedToken identical to the original invite token instead of enforcing token rotation. A crafted confirmation therefore preserves a previously issued token for reuse, bypassing the intended single-use integrity control.

CVSS severity3.7
Low
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in Mattermost 10.11.0 through 10.11.13 and 11.5.0 through 11.5.1 allows remote authenticated users to reuse invite tokens. Remote cluster invite confirmation accepts a RefreshedToken identical to the original invite token instead of enforcing token rotation. A crafted confirmation therefore preserves a previously issued token for reuse, bypassing the intended single-use integrity control.

The record

CVE
CVE-2026-4273
Published
May 18, 2026
Updated
May 18, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-863, T1550.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 18, 2026CVE publishedPublication date reported by the CVE source.
  2. May 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.11.0 <=10.11.13
  2. Affected versionversion=11.5.0 <=11.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.13; version=11.5.0 <=11.5.1

Published CVSS scores

4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
3.7Mattermost, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1550.001Application Access Token

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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