CVE-2019-20884Network attack vector

Unintended cross-post file association

Published Jun 19, 2020 · Updated Aug 5, 2024

Improper file attachment handling in Mattermost Server before 5.8.0 allows remote attackers to associate one file with multiple posts. Mattermost has not published the vulnerable function or the validation error that permits the cross-post association. No authentication or user interaction is required; the reported consequence is limited to unintended file-to-post associations.

CVSS severity5.3
Medium
EPSS probability0.81%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper file attachment handling in Mattermost Server before 5.8.0 allows remote attackers to associate one file with multiple posts. Mattermost has not published the vulnerable function or the validation error that permits the cross-post association. No authentication or user interaction is required; the reported consequence is limited to unintended file-to-post associations.

The record

CVE
CVE-2019-20884
Published
Jun 19, 2020
Updated
Aug 5, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1565.001
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

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
5.3NIST NVDCVSS: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 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

T1565.001Stored Data Manipulation

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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