CVE-2018-21265Network attack vector

Unauthorized browser permissions via origin policy mishandling

Published Jun 19, 2020 · Updated Aug 5, 2024

Origin validation failure in Mattermost Desktop App before 4.0.0 allows remote attackers to obtain browser permissions via web content. The Electron session permission-request path fails to preserve the Same Origin Policy when setPermissionRequestHandler handles video, audio, or notification requests. A remote origin loaded in the desktop client can therefore receive authorization outside its origin boundary, changing permission-controlled behavior without authentication or user interaction.

CVSS severity5.3
Medium
EPSS probability0.77%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Origin validation failure in Mattermost Desktop App before 4.0.0 allows remote attackers to obtain browser permissions via web content. The Electron session permission-request path fails to preserve the Same Origin Policy when setPermissionRequestHandler handles video, audio, or notification requests. A remote origin loaded in the desktop client can therefore receive authorization outside its origin boundary, changing permission-controlled behavior without authentication or user interaction.

The record

CVE
CVE-2018-21265
Published
Jun 19, 2020
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-732
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 19, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.3NVDCVSS:3.1/AV:N/AC:L/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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-732Incorrect Permission Assignment for Critical Resource

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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