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01 Record

CVE-2026-26233

Denial of Service via HTTP/2 single packet attack on login endpoint

MediumPUBLISHEDCNA: Mattermost
CNA base score4.3 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

02 Description

Denial of Service via HTTP/2 single packet attack on login endpoint

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.
  • AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
  • 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
0.31% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 23.6% of scored records. A rank, not a probability.
NVD base score
6.5 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD analysis status
Analyzed. NVD last modified this record on 2026-06-17.
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
2026-03-25 16:24Z7 MO AGO
Last updated
2026-03-27 14:59Z7 MO AGO
Reserved
2026-02-23
Assigning CNA
Mattermost
Record state
PUBLISHED
Severity
Medium (CVSS 4.3)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
Weaknesses
  • CWE-400Uncontrolled Resource ConsumptionClass
Data version
5.2
Document digest
bb78da899f4df9e8f2f23428bdc6ece0455e23988e98335b47120ff5f3feeef3

05 Affected products

VendorProductVersionsPlatforms
MattermostMattermost11.4.0 to 11.4.0, 11.3.0 to 11.3.1, 11.2.0 to 11.2.3, 10.11.0 to 10.11.11—

06 References

07 Remediation

Update Mattermost to versions 11.5.0, 11.4.1, 11.3.2, 11.2.4, 10.11.12 or higher.