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Description

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

PUBLISHED Reserved 2026-04-07 | Published 2026-05-22 | Updated 2026-05-22 | Assigner Mattermost




MEDIUM: 6.5CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Problem types

CWE-400 Uncontrolled Resource Consumption

Product status

Default status
unaffected

11.6.0 (semver)
affected

11.5.0 (semver)
affected

11.5.0 (semver)
affected

11.4.0 (semver)
affected

10.11.0 (semver)
affected

11.7.0
unaffected

11.6.1
unaffected

11.5.3
unaffected

11.5.4
unaffected

11.4.5
unaffected

10.11.15
unaffected

Credits

ZephrFish finder

References

mattermost.com/security-updates (MMSA-2026-00648) vendor-advisory

cve.org (CVE-2026-5755)

nvd.nist.gov (CVE-2026-5755)

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