synced 9 MIN AGO
01 Record

CVE-2026-18799

Mattermost Server fails to restrict Slack import account binding, allowing team admins to forge posts as existing users

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

02 Description

Mattermost Server fails to restrict Slack import account binding, allowing team admins to forge posts as existing users

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
0.19% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 9.4% of scored records. A rank, not a probability.
NVD base score
4.3 (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:L/A:N
NVD analysis status
Awaiting Analysis. NVD last modified this record on 2026-10-16.
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
2026-10-16 07:16Z13 DAYS AGO
Last updated
2026-10-16 11:28Z12 DAYS AGO
Reserved
2026-08-04
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:L/A:N
Weaknesses
Data version
5.2
Document digest
19031ecaddef1152bae248530ad0b5ee90536572a54a3446f28baed85d41760f

05 Affected products

VendorProductVersionsPlatforms
MattermostMattermost11.10.0 to 11.10.0, 11.7.0 to 11.7.9, 11.9.0 to 11.9.1, 11.8.0 to 11.8.5—

06 References

07 Remediation

Update Mattermost to versions 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 or higher.