CVE-2021-37866

Account takeover via reusable logged-out session tokens

Published Jan 18, 2022 · Updated Dec 6, 2024

Insufficient session expiration in Mattermost Boards 0.10.0 and earlier allows attackers to reuse a logged-out user's session token. The logout path fails to revoke the server-side session, while the browser retains its token in local storage without an expiration time. Exploitation requires obtaining the retained token, such as through cross-site scripting, and grants authorization as the victim with resulting account-data exposure.

CVSS severity4.7
Medium
EPSS probability0.72%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Insufficient session expiration in Mattermost Boards 0.10.0 and earlier allows attackers to reuse a logged-out user's session token. The logout path fails to revoke the server-side session, while the browser retains its token in local storage without an expiration time. Exploitation requires obtaining the retained token, such as through cross-site scripting, and grants authorization as the victim with resulting account-data exposure.

The record

CVE
CVE-2021-37866
Published
Jan 18, 2022
Updated
Dec 6, 2024
Vendor
Mattermost
Product
Mattermost Boards
Classifications
CWE-613, T1550.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 18, 2022CVE publishedPublication date reported by the CVE source.
  2. Dec 6, 2024Record 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=unspecified <=0.10.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Mattermost · Mattermost Boardsversion=unspecified <=0.10.0

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
4.7Mattermost, Inc.CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N
5.0NIST NVDAV:N/AC:L/Au:N/C:P/I:N/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)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-613Insufficient Session Expiration
T1550.004Use Alternate Authentication Material: Web Session Cookie

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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