CVE-2026-33410
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedDiscourse is an open-source discussion platform. Versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 have two authorization issues in the chat direct message API. First, when creating a direct message channel or adding users to an existing one, the `target_groups` parameter was passed directly to the user resolution query without checking group or member visibility for the acting user. An authenticated chat user could craft an API request with a known private/hidden group name and receive a channel containing that group's members, leaking their identities. Second, `can_chat?` only checked group membership, not the `chat_enabled` user preference. A chat-disabled user could create or query DM channels between other users via the direct messages API, potentially exposing private `last_message` content from the serialized channel response. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. No known workarounds are available.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceDiscourse versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain two authorization bypass flaws in the chat direct message API: the `target_groups` parameter is passed to user resolution without group/member visibility checks, allowing authenticated users to leak private group member identities by including known hidden group names; separately, `can_chat?` only verifies group membership but ignores the `chat_enabled` user preference, enabling chat-disabled users to create/query DM channels and access private `last_message` content from serialized responses.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 2026.1.0, < 2026.1.2>= 2026.2.0, < 2026.2.1= 2026.3.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Identify installed Discourse versionAccess the Discourse admin dashboard /about page or check the version file in the Discourse installation directory (typically in the Git repo or via './discourse version' command if using the official installer)Affected if Version is >= 2026.1.0 and < 2026.1.2, OR >= 2026.2.0 and < 2026.2.1, OR equals 2026.3.0
-
Verify group membership leakage via target_groups parameterUsing an authenticated user account, attempt to create a chat direct message with the target_groups parameter set to a known private/hidden group name. Inspect whether the API response reveals private group member identities that the requesting user should not have access to.Affected if The API returns private group member details or allows enumeration of hidden group members through the target_groups parameter
-
Verify chat_enabled preference is enforced for DM channel creationCreate or modify a test user with chat_enabled preference disabled (typically found in user preferences). Attempt to create a chat direct message channel as that user. Also query existing DM channels as that user and inspect the serialized response for last_message content.Affected if Users with chat_enabled set to false can successfully create/query DM channels and access last_message content from the API responses
A user is affected if running a vulnerable Discourse version (2026.1.0-2026.1.1, 2026.2.0-2026.2.0, or 2026.3.0) AND either private group member information is exposed via the target_groups parameter OR users with chat disabled can still access DM channels and messages.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2026.1.22026.2.1
Upgrade Discourse to version 2026.3.0-latest.1, 2026.2.1, 2026.1.2 or later to apply the patched authorization checks for both group visibility and the chat_enabled user preference.
Upgrade to Discourse 2026.1.2 (if currently on 2026.1.x), 2026.2.1 (if currently on 2026.2.x), or 2026.3.0-latest.1 (if currently on 2026.3.0)
- Confirm current Discourse version by checking the /admin dashboard or running `git log` in the container
- Take a complete backup of the Discourse database and site settings before upgrading
- For Docker-based installations: run `./launcher stop app` to stop the container
- Pull the latest Discourse Docker image or update via the package manager
- Run `./launcher rebuild app` to apply the upgrade
- After the container restarts, verify the new version in /admin dashboard
- Confirm the chat direct message functionality works correctly after upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-33410 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-33410 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data