CVE-2026-91156Network attack vectorHinoki check available

Message disclosure via incomplete MessageBus audience authorization

Published Oct 14, 2026 · Updated Oct 14, 2026

Authorization bypass in Discourse Chat allows remote authenticated users to read restricted messages through MessageBus subscriptions. The Chat publisher calculates the audience for read-restricted category channels from category visibility without also enforcing the site's Chat group restrictions. An account with category access but no Chat eligibility receives live messages and recent backlog content, but cannot retrieve full channel history through the Chat API or create or modify messages.

CVSS severityUnavailable
Unscored
EPSS probability0.48%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Get started

Summary

What happened

Authorization bypass in Discourse Chat allows remote authenticated users to read restricted messages through MessageBus subscriptions. The Chat publisher calculates the audience for read-restricted category channels from category visibility without also enforcing the site's Chat group restrictions. An account with category access but no Chat eligibility receives live messages and recent backlog content, but cannot retrieve full channel history through the Chat API or create or modify messages.

The record

CVE
CVE-2026-91156
Published
Oct 14, 2026
Updated
Oct 14, 2026
Vendor
Discourse
Product
Discourse
Classifications
T1213
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 14, 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=< 2026.1.9
  2. Affected versionversion=>= 2026.7.0-latest, < 2026.7.3
  3. Affected versionversion=>= 2026.8.0-latest, < 2026.8.1
  4. Affected versionversion=>= 2026.9.0-latest, < 2026.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Discourse · Discourseversion=< 2026.1.9; version=>= 2026.7.0-latest, < 2026.7.3; version=>= 2026.8.0-latest, < 2026.8.1; version=>= 2026.9.0-latest, < 2026.9.0

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

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

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1213Data from Information Repositories

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

Get started to see how Hinoki identifies affected software and validates exploitability in your environment.

Get started