CVE-2026-27656
- Source
- https://cve.org/CVERecord?id=CVE-2026-27656
- Import Source
- https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-27656.json
- JSON Data
- https://api.osv.dev/v1/vulns/CVE-2026-27656
- Aliases
- Downstream
- Related
- Published
- 2026-03-25T16:28:29.739Z
- Modified
- 2026-07-31T18:29:59.876398786Z
- Severity
-
- 5.7 (Medium) CVSS_V3 - CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:N CVSS Calculator
- Summary
- Account Takeover via Substring Matching in OpenID Connect Authentication
- Details
-
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
- Database specific
{ "cwe_ids": [ "CWE-303" ], "cna_assigner": "Mattermost", "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/27xxx/CVE-2026-27656.json", "unresolved_ranges": [ { "source": "AFFECTED_FIELD", "extracted_events": [ { "introduced": "11.4.0" }, { "last_affected": "11.4.0" }, { "introduced": "11.3.0" }, { "last_affected": "11.3.1" }, { "introduced": "11.2.0" }, { "last_affected": "11.2.3" }, { "introduced": "10.11.0" }, { "last_affected": "10.11.11" } ] } ] }- References
Affected packages
Git / github.com/mattermost/mattermost
Affected ranges
- Type
- GIT
- Repo
- https://github.com/mattermost/mattermost
- Events
-
IntroducedFixedIntroducedFixedIntroducedFixedIntroducedFixed
- Database specific
{ "source": "CPE_RANGE", "cpe": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "extracted_events": [ { "introduced": "10.11.0" }, { "fixed": "10.11.12" }, { "introduced": "11.2.0" }, { "fixed": "11.2.4" }, { "introduced": "11.3.0" }, { "fixed": "11.3.2" }, { "introduced": "11.4.0" }, { "fixed": "11.4.1" } ] }
Affected versions
@mattermost/client@10.*
@mattermost/client@10.11.0
@mattermost/client@11.*
@mattermost/client@11.3.0
@mattermost/client@11.4.0
@mattermost/types@10.*
@mattermost/types@10.11.0
@mattermost/types@11.*
@mattermost/types@11.3.0
@mattermost/types@11.4.0
mattermost-redux@10.*
mattermost-redux@10.11.0
mattermost-redux@11.*
mattermost-redux@11.3.0
mattermost-redux@11.4.0
v10.*
v10.11.0
v10.11.0-rc3
v10.11.1
v10.11.1-rc1
v10.11.10
v10.11.11
v10.11.11-rc1
v10.11.11-rc2
v10.11.2
v10.11.2-rc1
v10.11.2-rc2
v10.11.3
v10.11.4
v10.11.4-rc1
v10.11.4-rc2
v10.11.4-rc3
v10.11.5
v10.11.6
v10.11.7
v10.11.8
v10.11.9
v10.11.9-rc1
v11.*
v11.2.0
v11.2.1
v11.2.1-rc1
v11.2.2
v11.2.3
v11.3.0
v11.3.0-rc3
v11.3.0-rc4
v11.3.1
v11.3.1-rc1
v11.4.0
v11.4.0-rc3