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.
- 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
- CWE-862Missing AuthorizationClass
- Data version
- 5.2
- Document digest
- 19031ecaddef1152bae248530ad0b5ee90536572a54a3446f28baed85d41760f
05 Affected products
VendorProductVersionsPlatforms
06 References
- mattermost.comMMSA-2026-00757https://mattermost.com/security-updates
07 Remediation
Update Mattermost to versions 11.11.0, 11.10.1, 11.7.10, 11.9.2, 11.8.6 or higher.