CVE-2026-3109Network attack vector

Meeting-state corruption via replayed Zoom webhooks

Published Mar 26, 2026 · Updated Mar 26, 2026

Webhook replay in the Zoom plugin for Mattermost 10.11.11 and earlier allows attackers to corrupt meeting state via signed requests. The server/webhook.go signature verifier authenticates the timestamp and body but previously never checks whether x-zm-request-timestamp is fresh. Exploitation requires access to a previously valid signed Zoom webhook, and the deployment must have Zoom webhook events configured.

CVSS severity2.2
Low
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Webhook replay in the Zoom plugin for Mattermost 10.11.11 and earlier allows attackers to corrupt meeting state via signed requests. The server/webhook.go signature verifier authenticates the timestamp and body but previously never checks whether x-zm-request-timestamp is fresh. Exploitation requires access to a previously valid signed Zoom webhook, and the deployment must have Zoom webhook events configured.

The record

CVE
CVE-2026-3109
Published
Mar 26, 2026
Updated
Mar 26, 2026
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-754, T1565.001
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Mar 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <=10.11.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Mattermost · Mattermostversion=0 <=10.11.11

Published CVSS scores

2.2Mattermost, Inc.CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
T1565.001Stored Data Manipulation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo