CVE-2026-5755: Denial of service via crafted TIFF file upload

Published May 22, 2026
·
Updated

Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.2, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, 10.11.x <= 10.11.14 fail to validate the TIFF IFD offset in the image header before allocating memory, which allows authenticated users with file upload or posting permissions to cause a denial of service (server OOM) via uploading a crafted TIFF file or posting a URL that serves one.. Mattermost Advisory ID: MMSA-2026-00648

Affected Software

1 affected component
Mattermost Mattermost<=11.6.0, <=11.5.2, <=11.5.3, <=11.4.4, <=10.11.14

Remediation

Information

Update Mattermost to versions 11.7.0, 11.6.1, 11.5.3, 11.5.4, 11.4.5, 10.11.15 or higher.

Event History

May 22, 2026
CVE Published
via MITRE·10:18 AM
Data Sourced
via MITRE·10:18 AM
RemedyDescriptionSeverityWeakness
Free Weekly Intel

Don't miss critical vulnerabilities

Join thousands of security professionals who receive our weekly digest of trending CVEs, zero-days, and exploited vulnerabilities.

No spam. Unsubscribe anytime.

Frequently Asked Questions

1

What is the severity of CVE-2026-5755?

CVE-2026-5755 has a medium severity rating of 6.5.

2

How do I fix CVE-2026-5755?

To fix CVE-2026-5755, you should update Mattermost to version 11.7.0, 11.6.1, 11.5.3, 11.5.4, 11.4.5, 10.11.15 or higher.

3

What system versions are affected by CVE-2026-5755?

CVE-2026-5755 affects Mattermost versions 11.6.x <= 11.6.0, 11.5.x <= 11.5.2, 11.5.x <= 11.5.3, 11.4.x <= 11.4.4, and 10.11.x <= 10.11.14.

4

What type of attack is CVE-2026-5755 associated with?

CVE-2026-5755 is associated with a denial of service attack via crafted TIFF file uploads.

5

Who can exploit CVE-2026-5755?

CVE-2026-5755 can be exploited by authenticated users who have file upload or posting permissions.

Company

Resources

Contact

SecAlerts Pty Ltd.
132 Wickham Terrace
Fortitude Valley,
QLD 4006, Australia
info@secalerts.co
By using SecAlerts services, you agree to our services end-user license agreement. This website is safeguarded by reCAPTCHA and governed by the Google Privacy Policy and Terms of Service. All names, logos, and brands of products are owned by their respective owners, and any usage of these names, logos, and brands for identification purposes only does not imply endorsement. If you possess any content that requires removal, please get in touch with us.
© 2026 SecAlerts Pty Ltd.
ABN: 70 645 966 203, ACN: 645 966 203