CVE-2025-20088Network attack vector

Authenticated client crash via unchecked post-property access

Published Jan 15, 2025 · Updated Feb 12, 2025

Improper input validation in affected Mattermost 9.11, 10.0, 10.1, and 10.2 releases allows remote authenticated users to crash web clients. The web client reads post-controlled record keys without own-property checks and passes attachment field values to string handling without validating their type. An account able to publish a crafted post is required, and the documented consequence is loss of client availability rather than data disclosure or modification.

CVSS severity6.5
Medium
EPSS probability0.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in affected Mattermost 9.11, 10.0, 10.1, and 10.2 releases allows remote authenticated users to crash web clients. The web client reads post-controlled record keys without own-property checks and passes attachment field values to string handling without validating their type. An account able to publish a crafted post is required, and the documented consequence is loss of client availability rather than data disclosure or modification.

The record

CVE
CVE-2025-20088
Published
Jan 15, 2025
Updated
Feb 12, 2025
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-1287, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 15, 2025CVE publishedPublication date reported by the CVE source.
  2. Feb 12, 2025Record 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=10.0.0 <=10.0.3
  2. Affected versionversion=10.1.0 <=10.1.3
  3. Affected versionversion=10.2.0
  4. Affected versionversion=9.11.0 <=9.11.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.0.0 <=10.0.3; version=10.1.0 <=10.1.3; version=10.2.0; version=9.11.0 <=9.11.5

Published CVSS scores

6.5MattermostCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-1287Improper Validation of Specified Type of Input
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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