CVE-2025-55035Network attack vector

Client denial of service via unclosable modal

Published Oct 16, 2025 · Updated Oct 16, 2025

Denial of service in Mattermost Desktop App 5.13.0 and earlier allows remote attackers to block app use through a malicious server. The Desktop App's modal handling leaves the basic-authentication dialog from the attacker-controlled server unclosable and blocks the rest of the interface. Exploitation requires user interaction to configure the malicious server and an existing server that uses basic authentication; the consequence is interruption of Desktop App use rather than server outage or data loss.

CVSS severity6.1
Medium
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Mattermost Desktop App 5.13.0 and earlier allows remote attackers to block app use through a malicious server. The Desktop App's modal handling leaves the basic-authentication dialog from the attacker-controlled server unclosable and blocks the rest of the interface. Exploitation requires user interaction to configure the malicious server and an existing server that uses basic authentication; the consequence is interruption of Desktop App use rather than server outage or data loss.

The record

CVE
CVE-2025-55035
Published
Oct 16, 2025
Updated
Oct 16, 2025
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-754
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 16, 2025CVE publishedPublication date reported by the CVE source.
  2. Oct 16, 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=0 <=5.0.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mattermost · Mattermostversion=0 <=5.0.13

Published CVSS scores

6.1MattermostCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/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.

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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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions

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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