CVE-2019-20887Network attack vector

Post disclosure via ignored flags API permissions

Published Jun 19, 2020 · Updated Aug 5, 2024

Missing authorization in Mattermost Server before 5.7.1, 5.6.4, 5.5.3, and 4.10.6 allows remote authenticated users to read intra-team posts. The post-delivery decision fails to enforce the flags API permission that governs whether a user is allowed to receive those posts. A valid low-privilege account is required, and the exposed data is limited to intra-team post content available through the flawed delivery path.

CVSS severity4.3
Medium
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in Mattermost Server before 5.7.1, 5.6.4, 5.5.3, and 4.10.6 allows remote authenticated users to read intra-team posts. The post-delivery decision fails to enforce the flags API permission that governs whether a user is allowed to receive those posts. A valid low-privilege account is required, and the exposed data is limited to intra-team post content available through the flawed delivery path.

The record

CVE
CVE-2019-20887
Published
Jun 19, 2020
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-862, T1213
Attack vector
network
Privileges
authenticated

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 privilegesauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

4.0NIST NVDAV:N/AC:L/Au:S/C:P/I:N/A:N
4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/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.

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-862Missing Authorization
T1213Data from Information Repositories

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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