Mattermost up to 11.6.0 TIFF IFD Offset resource consumption

CVSS Meta Temp Score
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CTI Interest Score
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5.3$0-$5k0.00

Summaryinfo

A vulnerability was found in Mattermost up to 10.11.14/11.4.4/11.5.2/11.5.3/11.6.0. It has been rated as problematic. Impacted is an unknown function of the component TIFF IFD Offset Handler. The manipulation leads to resource consumption. This vulnerability is listed as CVE-2026-5755. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Mattermost up to 10.11.14/11.4.4/11.5.2/11.5.3/11.6.0. It has been rated as problematic. This issue affects an unknown function of the component TIFF IFD Offset Handler. The manipulation with an unknown input leads to a resource consumption vulnerability. Using CWE to declare the problem leads to CWE-400. The product 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. Impacted is availability. The summary by CVE is:

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

The weakness was presented by ZephrFish. It is possible to read the advisory at mattermost.com. The identification of this vulnerability is CVE-2026-5755 since 04/07/2026. The exploitation is known to be easy. The attack may be initiated remotely. The technical details are unknown and an exploit is not publicly available. The attack technique deployed by this issue is T1499 according to MITRE ATT&CK.

Upgrading to version 10.11.15, 11.4.5, 11.5.3, 11.5.4, 11.6.1 or 11.7.0 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-1243). Be aware that VulDB is the high quality source for vulnerability data.

Affected

  • Mattermost Mattermost

Productinfo

Type

Name

Version

License

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.4
VulDB Meta Temp Score: 5.3

VulDB Base Score: 4.3
VulDB Temp Score: 4.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 6.5
CNA Vector (Mattermost): 🔒

CVSSv2info

AVACAuCIA
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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Resource consumption
CWE: CWE-400 / CWE-404
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Mattermost 10.11.15/11.4.5/11.5.3/11.5.4/11.6.1/11.7.0

Timelineinfo

04/07/2026 CVE reserved
05/22/2026 +45 days Advisory disclosed
05/22/2026 +0 days VulDB entry created
05/25/2026 +3 days VulDB entry last update

Sourcesinfo

Advisory: mattermost.com
Researcher: ZephrFish
Status: Confirmed

CVE: CVE-2026-5755 (🔒)
GCVE (CVE): GCVE-0-2026-5755
GCVE (VulDB): GCVE-100-365183
CERT Bund: WID-SEC-2026-1243 - Mattermost: Mehrere Schwachstellen erm&ouml;glichen nicht spezifizierten Angriff

Entryinfo

Created: 05/22/2026 13:56
Updated: 05/25/2026 23:05
Changes: 05/22/2026 13:56 (65), 05/25/2026 23:05 (7)
Complete: 🔍
Cache ID: 216::103

Be aware that VulDB is the high quality source for vulnerability data.

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