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01 Record

CVE-2026-5740

Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server

HighPUBLISHEDCNA: Mattermost
CNA base score7.5 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

02 Description

Unauthenticated WebSocket binary frame causes denial of service in Mattermost Server

03 Exploitation and scoring

Exploitation
Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.
SSVC decision
  • ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.34% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 27.2% of scored records. A rank, not a probability.
NVD base score
7.5 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD analysis status
Analyzed. NVD last modified this record on 2026-07-23.
Red Hat severity
No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-05-22 10:22Z5 MO AGO
Last updated
2026-05-22 12:14Z5 MO AGO
Reserved
2026-04-07
Assigning CNA
Mattermost
Record state
PUBLISHED
Severity
High (CVSS 7.5)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weaknesses
  • CWE-789Memory Allocation with Excessive Size ValueVariant
Data version
5.2
Document digest
fc436e4e7bd285feae0bb3acc5caa12c3fef19c8c687c530731773564a0a1639

05 Affected products

VendorProductVersionsPlatforms
MattermostMattermost11.6.0 to 11.6.0, 11.5.0 to 11.5.3, 11.4.0 to 11.4.4, 10.11.0 to 10.11.14—

06 References

07 Remediation

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