Mattermost <=11.6.0 TIFF IFD OOM DoS via Crafted TIFF
CVE-2026-5755 Published on May 22, 2026
Denial of service via crafted TIFF file upload
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
Vulnerability Analysis
CVE-2026-5755 can be exploited with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is a Resource Exhaustion Vulnerability?
The software does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
CVE-2026-5755 has been classified to as a Resource Exhaustion vulnerability or weakness.
Products Associated with CVE-2026-5755
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Affected Versions
Mattermost:- Version 11.6.0, <= 11.6.0 is affected.
- Version 11.5.0, <= 11.5.2 is affected.
- Version 11.5.0, <= 11.5.3 is affected.
- Version 11.4.0, <= 11.4.4 is affected.
- Version 10.11.0, <= 10.11.14 is affected.
- Version 11.7.0 is unaffected.
- Version 11.6.1 is unaffected.
- Version 11.5.3 is unaffected.
- Version 11.5.4 is unaffected.
- Version 11.4.5 is unaffected.
- Version 10.11.15 is unaffected.