CVE-2026-26246Network attack vector

Denial of service via unbounded PSD allocation

Published Mar 16, 2026 · Updated Mar 16, 2026

Denial of service in Mattermost 10.11.0 through 10.11.10, 11.2.0 through 11.2.2, and 11.3.0 allows remote authenticated users to exhaust memory. The server's PSD inline-preview path processes attacker-controlled file data without effectively bounding the resulting memory allocation. Any authenticated account able to upload an attachment can exhaust server memory and interrupt the service.

CVSS severity4.3
Medium
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Denial of service in Mattermost 10.11.0 through 10.11.10, 11.2.0 through 11.2.2, and 11.3.0 allows remote authenticated users to exhaust memory. The server's PSD inline-preview path processes attacker-controlled file data without effectively bounding the resulting memory allocation. Any authenticated account able to upload an attachment can exhaust server memory and interrupt the service.

The record

CVE
CVE-2026-26246
Published
Mar 16, 2026
Updated
Mar 16, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-789, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.11.0 <=10.11.10
  2. Affected versionversion=11.2.0 <=11.2.2
  3. Affected versionversion=11.3.0 <=11.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.11.0 <=10.11.10; version=11.2.0 <=11.2.2; version=11.3.0 <=11.3.0

Published CVSS scores

4.3Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

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-789Memory Allocation with Excessive Size Value
T1499.004Application or System Exploitation

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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo