GHSA-5gmf-x7hg-97wf: Mattermost doesn't filter nil elements from outgoing webhook attachment payloads before processing
Mattermost versions 10.11.0 through 10.11.14, 11.4.0 through 11.4.4, 11.5.0 through 11.5.3, and 11.6.0 are vulnerable to a denial of service caused by failure to filter nil elements from outgoing webhook attachment payloads. An authenticated user can send a crafted webhook callback response containing a null attachment entry, which causes the server process to terminate.
AI Analysis
Technical Summary
Mattermost server versions 10.11.x <= 10.11.14, 11.4.x <= 11.4.4, 11.5.x <= 11.5.3, and 11.6.x <= 11.6.0 do not properly filter nil elements from outgoing webhook attachment payloads before processing. This vulnerability allows an authenticated user to trigger a denial of service by sending a specially crafted webhook callback response with a null attachment entry, leading to server process termination. The issue is tracked as CVE-2026-4915 and is categorized under CWE-754.
Potential Impact
The vulnerability results in a denial of service (DoS) condition by causing the Mattermost server process to terminate unexpectedly when processing webhook payloads containing null attachment entries. There is no impact on confidentiality or integrity according to the available data.
Mitigation Recommendations
Patch status is not yet confirmed — check the Mattermost advisory MMSA-2026-00641 for current remediation guidance. Until a patch is available, consider restricting webhook usage to trusted users and monitoring webhook configurations to prevent exploitation.
GHSA-5gmf-x7hg-97wf: Mattermost doesn't filter nil elements from outgoing webhook attachment payloads before processing
Description
Mattermost versions 10.11.0 through 10.11.14, 11.4.0 through 11.4.4, 11.5.0 through 11.5.3, and 11.6.0 are vulnerable to a denial of service caused by failure to filter nil elements from outgoing webhook attachment payloads. An authenticated user can send a crafted webhook callback response containing a null attachment entry, which causes the server process to terminate.
CVSS v3.1
Affected software
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Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Mattermost server versions 10.11.x <= 10.11.14, 11.4.x <= 11.4.4, 11.5.x <= 11.5.3, and 11.6.x <= 11.6.0 do not properly filter nil elements from outgoing webhook attachment payloads before processing. This vulnerability allows an authenticated user to trigger a denial of service by sending a specially crafted webhook callback response with a null attachment entry, leading to server process termination. The issue is tracked as CVE-2026-4915 and is categorized under CWE-754.
Potential Impact
The vulnerability results in a denial of service (DoS) condition by causing the Mattermost server process to terminate unexpectedly when processing webhook payloads containing null attachment entries. There is no impact on confidentiality or integrity according to the available data.
Mitigation Recommendations
Patch status is not yet confirmed — check the Mattermost advisory MMSA-2026-00641 for current remediation guidance. Until a patch is available, consider restricting webhook usage to trusted users and monitoring webhook configurations to prevent exploitation.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- GHSA-5gmf-x7hg-97wf
- Osv Schema Version
- 1.4.0
- Aliases
- ["CVE-2026-4915"]
- Ecosystems
- ["Go"]
- Database Specific Severity
- MODERATE
- Cvss Version
- 3.1
Threat ID: 6a4452ee27e9c797198ec108
Added to database: 06/30/2026, 23:36:14 UTC
Last enriched: 06/30/2026, 23:55:24 UTC
Last updated: 07/01/2026, 00:20:10 UTC
Views: 3
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