VulnSocial

CVE-2026-27656Disclosure(mattermost / mattermost_server)

LOWCVSS 6.1 · MEDIUM

Signal is active with 1 mentions in latest observed window

Immediate actions

  • Track advisory updates for patch or workaround availability

Recommended action window: Monitor and triage in normal cycle

NVD description

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to properly validate user identity in the OpenID {{IsSameUser()}} comparison logic, which allows an attacker to take over arbitrary user accounts via an overly permissive substring matching flaw in the user discovery flow.. Mattermost Advisory ID: MMSA-2026-00590

mattermost CVEsBack to dashboard
0.0/ 10 priority

Sources & remediation

Vendor / third-party advisories
Weakness type (CWE)
CWE-303

Priority

LOW

Exploitation

NONE

PoC

NONE

Patch

NONE

Momentum

NONE

Are you affected?

If you run products in this scope, you should treat this CVE as relevant to your environment.

  • mattermost_server

Threat summary

  • 1 mentions across 1 observed day

What's happening

  • Technical details provided in 1 signal
  • Disclosure: 1 classified signal
  • 1 total mentions across 1 day

Affected systems

Vendors
mattermost
Products
mattermost_server

Deep dive

Activity timeline1 mentions / 1d
00111Mentions · 2026-03-25: 1Technical Details · 2026-03-25: 103-25
Signal classification1 categories
Disclosure
1100.0%
Referenced assets1 URL
By indicator
Full discourse1 post
  • CVE@CVEnew
    Disclosure

    CVE-2026-27656 Mattermost versions 11.4.x &lt;= 11.4.0, 11.3.x &lt;= 11.3.1, 11.2.x &lt;= 11.2.3, 10.11.x &lt;= 10.11.11 fail to properly validate user identity in the OpenID {{IsSameUser()}} c… https://www.cve.org/CVERecord?id=CVE-2026-27656

    Post summary

    This entry is a concise disclosure of a CVE affecting multiple Mattermost versions, noting a failure to validate user identity via OpenID, but it does not mention any PoC, exploit, active use, patch, or debunking.

    00000151
    56.8K followersView on X
CPE platform detail1 entries

1 of 1 entries

PartVendorProductVersionTarget SWTarget HW
Appmattermostmattermost_server---

Explore more

Back to dashboardmattermost CVEsmattermost_server vulnerabilities