CVE-2026-3472Network attack vector

Authenticated data exfiltration via Markdown image injection

Published Jun 26, 2026 · Updated Jun 26, 2026

Protection mechanism failure in affected Mattermost servers allows remote authenticated users to exfiltrate data through AI bot posts. AI bot tool results accept injected Markdown image syntax without the normal image-rendering restrictions, causing a victim's client to request an attacker-controlled URL. The attacker needs an authenticated account and a victim who renders the post; affected releases are 10.11.0 through 10.11.18, 11.5.0 through 11.5.6, and 11.6.0 through 11.6.3, and the reported impact is limited to data exfiltration.

CVSS severity3.5
Low
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Protection mechanism failure in affected Mattermost servers allows remote authenticated users to exfiltrate data through AI bot posts. AI bot tool results accept injected Markdown image syntax without the normal image-rendering restrictions, causing a victim's client to request an attacker-controlled URL. The attacker needs an authenticated account and a victim who renders the post; affected releases are 10.11.0 through 10.11.18, 11.5.0 through 11.5.6, and 11.6.0 through 11.6.3, and the reported impact is limited to data exfiltration.

The record

CVE
CVE-2026-3472
Published
Jun 26, 2026
Updated
Jun 26, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-693
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 26, 2026Record 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=10.11.0 <=10.11.18
  2. Affected versionversion=11.5.0 <=11.5.6
  3. Affected versionversion=11.6.0 <=11.6.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.18; version=11.5.0 <=11.5.6; version=11.6.0 <=11.6.3

Published CVSS scores

3.5Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:R/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.

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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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-693Protection Mechanism Failure

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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