> ## Content Index > Fetch the complete content index at: https://f4n6.co.uk/llms.txt > Use this file to discover other available public pages before exploring further. # Mattermost Server 11.7.x vulnerability requires urgent patching - URL: https://f4n6.co.uk/security-feed/mattermost-server-11-7-x-vulnerability-requires-urgent-patching/ - Published: 2026-10-23T18:13:57.000Z - Updated: 2026-10-23T18:13:57.000Z - Author: Jeff Davies - Tags: #security-feed ## 1\. Executive summary CERT-FR published advisory CERTFR-2026-AVI-1368 on 23 October 2026 covering a vulnerability in Mattermost Server versions 11.7.x earlier than 11.7.14, fixed in vendor bulletin MMSA-2026-00708 of 22 October 2026\. The vulnerability type, CVSS score, CWE and exploitation status are not stated by the publisher or by CERT-FR, and no CVE identifier has been assigned in the material available. The item is the latest in a run of Mattermost advisories through October 2026 (CERTFR-2026-AVI-1328, -1338, -1344, -1348), which together move the fixed floor for the 11.7 branch from 11.7.12 to 11.7.14 within seven days. EMEA financial services firms running Mattermost as an internal collaboration platform should treat this as a patch-cycle item: the risk is concentrated in internet-exposed or federated deployments where an unauthenticated or low-privilege flaw would be reachable, and that reachability cannot be confirmed from the source. ## 2\. Regulatory framing No specific DORA/NIS2 article is directly engaged by this item. ## 3\. Technical analysis & attack chain CERT-FR does not describe the vulnerability mechanism. The advisory states only that the flaw lets an attacker "provoquer un problème de sécurité non spécifié par l'éditeur" (cause a security problem unspecified by the publisher), and directs readers to the Mattermost security bulletin for fixes. No attack chain can be reconstructed from the source, and none is presented here. What the source establishes: 1. Affected product: Mattermost Server, 11.7.x branch, versions earlier than 11.7.14. 2. Fixed version: 11.7.14, per vendor bulletin MMSA-2026-00708 dated 22 October 2026. 3. Publication: CERT-FR advisory dated 23 October 2026. The surrounding advisories give the patch context an administrator needs. CERTFR-2026-AVI-1338 (19 October 2026, MMSA-2026-00709) covered 11.7.x earlier than 11.7.12\. CERTFR-2026-AVI-1344 (20 October 2026)# 11.7.x earlier than 11.7.12 plus 11.8.x earlier than 11.8.6, 11.10.x earlier than 11.10.3 and 11.11.x earlier than 11.11.2\. CERTFR-2026-AVI-1348 (21 October 2026, MMSA-2026-00772 and MMSA-2026-00783) moved the 11.7 floor to 11.7.13\. This item moves it again to 11.7.14\. A host still on 11.7.11 or below is exposed to at least three separate published issues, not one. CERTFR-2026-AVI-1328 (16 October 2026) covers the Desktop App (6.2.x before 6.2.4, 6.3.x before 6.3.1, earlier than 6.4) and is a separate client-side track. The 11.7 branch is the only branch named in this item. The 11.8, 11.10 and 11.11 branches were addressed in the earlier advisories and are not restated here; administrators on those branches should confirm their fixed floor against the vendor bulletin rather than assume this advisory covers them. Confidence caveat: every technical fact above rests on CERT-FR advisories and the Mattermost bulletin references they cite. The vendor bulletins themselves were not retrieved for this note. The vulnerability class, whether authentication is required, whether the flaw is remotely reachable, and whether exploitation has been observed are all unknown. No CVE has been assigned in the available material, so no NVD, EPSS or CISA KEV position exists to report. Absence from KEV is not evidence of low risk; it reflects that no CVE identifier is available to check. ## 4\. Mitigation & containment P1 (within 24 hours) - Inventory every Mattermost Server instance and record its exact version. Any 11.7.x below 11.7.14 is in scope. Any 11.7.x below 11.7.13 is also exposed to the issues in CERTFR-2026-AVI-1348 and -1338 and should be treated as higher priority. - Upgrade 11.7.x instances to 11.7.14 using the vendor bulletin MMSA-2026-00708 at https://mattermost.com/security-updates/. Confirm the running version after restart, not just the package version. - Where an instance cannot be patched inside 24 hours, restrict network access to it. Remove direct internet exposure, restrict inbound access to the corporate range or VPN, and disable federation and public links if they are enabled and not required. P2 (within 72 hours) - Check the 11.8, 11.10 and 11.11 branches against their fixed floors from CERTFR-2026-AVI-1344 and -1348 (11.8.6, 11.10.3, 11.11.2) and patch any that are behind. - Update the Mattermost Desktop App to 6.4 or later, or to 6.2.4 / 6.3.1 on the respective branches, per CERTFR-2026-AVI-1328. - Review Mattermost server logs for the period since the earliest affected version was deployed for anomalous authentication, admin actions or plugin activity. The source gives no indicators to search on, so this is a baseline review, not a signature hunt. P3 (within 7 days) - Add Mattermost version currency to the standard patch reporting so that a branch falling more than one release behind is flagged. The October 2026 sequence shows three 11.7 fixes in seven days; a quarterly review would have missed all of them. - Confirm whether any Mattermost instance handles regulated or client data and whether its exposure profile justifies internet-facing deployment at all. ## 5\. Indicators of compromise No indicators of compromise available in the source material. ## 6\. Detection Insufficient indicators to author detection rules. ## 7\. Sources - ANSSI France CERT-FR, "Vulnérabilité dans Mattermost Server" (CERTFR-2026-AVI-1368), 23 October 2026\. https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1368/ - ANSSI France CERT-FR, "Vulnérabilité dans Mattermost Server" (CERTFR-2026-AVI-1338), 19 October 2026\. https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1338/ - ANSSI France CERT-FR, "Multiples vulnérabilités dans Mattermost Server" (CERTFR-2026-AVI-1348), 21 October 2026\. https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1348/ - ANSSI France CERT-FR, "Multiples vulnérabilités dans Mattermost Server" (CERTFR-2026-AVI-1344), 20 October 2026\. https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1344/ - ANSSI France CERT-FR, "Multiples vulnérabilités dans les produits Mattermost" (CERTFR-2026-AVI-1328), 16 October 2026\. https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1328/ - Mattermost security updates (vendor bulletins MMSA-2026-00708, -00709, -00772, -00783 and others referenced above). https://mattermost.com/security-updates/ ## 8\. Adverse Trace position Adverse Trace assesses this as a patch-cycle item of unknown severity. No CVSS score, CWE, CVE identifier or exploitation status is available from CERT-FR or the vendor bulletin reference, so we will not assign a severity we cannot support; the practical driver is that 11.7.x has received three fixes in seven days and any instance below 11.7.14 is behind. Client impact depends entirely on exposure: an internal-only Mattermost instance patched on the normal cycle is low urgency, while an internet-facing or federated instance on 11.7.11 or below carries the combined exposure of three published advisories and should be patched today. We will retrieve the Mattermost bulletins MMSA-2026-00708 and the earlier October bulletins to establish the vulnerability classes and any CVE identifiers, and will reissue this advisory with a scored assessment if that material supports one. Clients who cannot confirm their Mattermost version should contact us for a version sweep. --- [Read the original source →](https://www.cert.ssi.gouv.fr/avis/CERTFR-2026-AVI-1368/?ref=f4n6.co.uk) *Published via PulseTrace — Adverse Trace threat intelligence.*