CVE-2026-15814Network attack vectorHinoki check available

Authenticated service interruption via unbounded image decoding

Published Sep 14, 2026 · Updated Sep 14, 2026

Denial of service in Mattermost Server allows remote authenticated users to exhaust server memory through crafted image uploads. The image-decoding path allocates memory for uploaded image data without enforcing a ceiling on the amount allocated. Any authenticated account that can upload a profile picture, file attachment, team icon, or brand image can consume excessive memory and interrupt service.

CVSS severityUnavailable
Unscored
EPSS probability0.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Denial of service in Mattermost Server allows remote authenticated users to exhaust server memory through crafted image uploads. The image-decoding path allocates memory for uploaded image data without enforcing a ceiling on the amount allocated. Any authenticated account that can upload a profile picture, file attachment, team icon, or brand image can consume excessive memory and interrupt service.

The record

CVE
CVE-2026-15814
Published
Sep 14, 2026
Updated
Sep 14, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
T1499.003
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 14, 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 <=10.11.22
  2. Affected versionversion=11.7.0 <=11.7.7
  3. Affected versionversion=11.8.0 <=11.8.4
  4. Affected versionversion=11.9.0 <=11.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.22; version=11.7.0 <=11.7.7; version=11.8.0 <=11.8.4; version=11.9.0 <=11.9.0

Published CVSS scores

No CVSS assessment is available in this record.

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

T1499.003Application Exhaustion Flood

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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