Mattermost Server Vulnerability Affecting Versions Before 11.5.2
Summary
CERT-FR issued advisory CERTFR-2026-AVI-0465 on April 21, 2026, disclosing a vulnerability in Mattermost Server affecting versions 11.5.x prior to 11.5.2. The vulnerability allows an attacker to cause an unspecified security issue, according to Mattermost security bulletin MMSA-2026-00629. Affected organisations are advised to consult the vendor's security bulletin for available patches and remediation guidance.
“Une vulnérabilité a été découverte dans Mattermost Server.”
What changed
CERT-FR published a security advisory alerting organisations that Mattermost Server versions 11.5.x prior to 11.5.2 contain a vulnerability enabling an attacker to cause an unspecified security issue. The risk level is not specified by the vendor (Mattermost). The advisory references the vendor's own security bulletin MMSA-2026-00629 as the source of remediation information.
Organisations running affected Mattermost Server deployments should review the referenced Mattermost security update page and apply version 11.5.2 or later once patches are available. As a government-issued cybersecurity advisory, this document signals that French national authorities consider this vulnerability operationally relevant for covered entities and should be tracked alongside standard vulnerability management processes.
What to do next
- Consulter le bulletin de sécurité de l'éditeur pour l'obtention des correctifs
Archived snapshot
Apr 21, 2026GovPing captured this document from the original source. If the source has since changed or been removed, this is the text as it existed at that time.
Premier Ministre S.G.D.S.N
Agence nationale
de la sécurité des
systèmes d'information
Paris, le 21 avril 2026 N° CERTFR-2026-AVI-0465 Affaire suivie par: CERT-FR
Avis du CERT-FR
Objet: Vulnérabilité dans Mattermost Server
Gestion du document
| Référence | CERTFR-2026-AVI-0465 |
| Titre | Vulnérabilité dans Mattermost Server |
| Date de la première version | 21 avril 2026 |
| Date de la dernière version | 21 avril 2026 |
| Source(s) | Bulletin de sécurité Mattermost MMSA-2026-00629 du 20 avril 2026 |
Une gestion de version détaillée se trouve à la fin de ce document.
Risque
- Non spécifié par l'éditeur
Systèmes affectés
- Mattermost Server versions 11.5.x antérieures à 11.5.2
Résumé
Une vulnérabilité a été découverte dans Mattermost Server. Elle permet à un attaquant de provoquer un problème de sécurité non spécifié par l'éditeur.
Solutions
Se référer au bulletin de sécurité de l'éditeur pour l'obtention des correctifs (cf. section Documentation).
Documentation
- Bulletin de sécurité Mattermost MMSA-2026-00629 du 20 avril 2026
- https://mattermost.com/security-updates/
Gestion détaillée du document
- le 21 avril 2026 Version initiale
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