GHSA-3rhr-jr63-hwq5 CVE-2026-2578 GO-2026-4734
Mattermost fails to preserve the redacted state of burn-on-read posts during deletion
Medium
Go
- Severity
- 4.3 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.23%
- Chance of exploitation in the next 30 days. Higher than 13.60% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-201 Insertion of Sensitive Information Into Sent Data
- Fix
- Available
- 2 packages have a fixed version
Description
Mattermost versions 11.3.x <= 11.3.0 fail to preserve the redacted state of burn-on-read posts during deletion which allows channel members to access unrevealed burn-on-read message contents via the WebSocket post deletion event. Mattermost Advisory ID: MMSA-2026-00579
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| github.com/mattermost/mattermost-server | < 5.3.2-0.20260127062706-c6b205f0d770 |
5.3.2-0.20260127062706-c6b205f0d770 |
| github.com/mattermost/mattermost-server | >= 10.11.0-rc1, < 10.11.11 |
10.11.11 |
| github.com/mattermost/mattermost-server | >= 11.2.0-rc1, < 11.2.3 |
11.2.3 |
| github.com/mattermost/mattermost-server | >= 11.3.0-rc1, < 11.3.1 |
11.3.1 |
| github.com/mattermost/mattermost-server | >= 10.11.0-rc1+incompatible, < 10.11.11+incompatible>= 11.2.0-rc1+incompatible, < 11.2.3+incompatible>= 11.3.0-rc1+incompatible, < 11.3.1+incompatible |
10.11.11+incompatible11.2.3+incompatible11.3.1+incompatible |
| github.com/mattermost/mattermost-server/v5 | all versions |
No fix yet |
| github.com/mattermost/mattermost-server/v6 | all versions |
No fix yet |
| github.com/mattermost/mattermost/server/v8 | < 8.0.0-20260127062706-c6b205f0d770 |
8.0.0-20260127062706-c6b205f0d770 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
github.com/mattermost/mattermost-server Go → 5.3.2-0.20260127062706-c6b205f0d770
- go
go get github.com/mattermost/mattermost-server@v5.3.2-0.20260127062706-c6b205f0d770 && go mod tidy
github.com/mattermost/mattermost/server/v8 Go → 8.0.0-20260127062706-c6b205f0d770
- go
go get github.com/mattermost/mattermost/server/v8@v8.0.0-20260127062706-c6b205f0d770 && go mod tidy
Severity breakdown
CVSS 3.1 4.3
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Weakness
CWE-201: Insertion of Sensitive Information Into Sent Data
The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.
How to prevent it
- Requirements: Specify which data in the software should be regarded as sensitive. Consider which types of users should have access to which types of data.
- Implementation: Ensure that any possibly sensitive data specified in the requirements is verified with designers to ensure that it is either a calculated risk or mitigated elsewhere. Any information that is not necessary to the functionality should be removed in order to lower both the overhead and the possibility of security sensitive data being sent.
- System Configuration: Setup default error messages so that unexpected errors do not disclose sensitive information.
- Architecture and Design: Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-xmfh-3ccg-c9fx Mattermost has an Incorrect Authorization issue | Low | Also affects github.com/mattermost/mattermost-server |
| GHSA-h998-hxxj-8q83 Mattermost doesn't invalidate cached authentication state for active WebSocket connections during global session revocation | Medium | Also affects github.com/mattermost/mattermost-server |
| GHSA-g5vr-6pgg-74qv Mattermost doesn't enforce bot-specific permission checks on the user active status endpoint | Low | Also affects github.com/mattermost/mattermost-server |
| GHSA-jqgv-39mg-7c2r Mattermost doesn't authenticate Atlassian Connect installed callbacks, allowing a remote unauthenticated attacker to inject a rogue sharedSecret | Medium | Also affects github.com/mattermost/mattermost-server |
| GHSA-mxq2-5jpg-7474 Mattermost doesn't validate channel ownership of an existing subscription before applying edits | Medium | Also affects github.com/mattermost/mattermost-server |
| GHSA-2g8v-grq3-hq2g Mattermost doesn't enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler | Medium | Also affects github.com/mattermost/mattermost-server |
| GHSA-6hxm-w4hv-vgvw Mattermost doesn't require role-management authorization when setting the scheme_admin flag on group syncable link and patch endpoints | High | Also affects github.com/mattermost/mattermost-server |
| GHSA-9p44-r552-4wp9 Mattermost doesn't sanitize the Remote Cluster API response on PATCH operations | Medium | Also affects github.com/mattermost/mattermost-server |
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