CVE-2026-4265 json
Guest user can upload files without permission across teams
published 2026-03-16 7 mo ago modified 2026-06-17 4 mo ago also GHSA-xpvf-6qcc-9jqc , GO-2026-4749 , EUVD-2026-12425
- cvss
- 4.3
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 14%
- public exploits
- 0
- none known
Summary
Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to validate team-specific upload_file permissions which allows a guest user to post files in channels where they lack upload_file permission via uploading files in a team where they have permission and reusing the file metadata in a POST request to a different team. Mattermost Advisory ID: MMSA-2025-00553
Patch / fix
- go github.com/mattermost/mattermost/server/v8 8.0.0-20260107144005-c7f6efdfb035
- go github.com/mattermost/mattermost-server 5.3.2-0.20260107144005-c7f6efdfb035, 10.11.11, 10.11.11+incompatible, 11.2.3, 11.2.3+incompatible, 11.3.1, 11.3.1+incompatible
- Mattermost Mattermost 10.11.11, 11.2.3, 11.3.1, 11.4.0
- govulncheck-vulndb openSUSE Leap 15.6 0.0.20260326T203309-150000.1.155.2
suse advisories SUSE-SU-2026:1135-1
- govulncheck-vulndb openSUSE Leap 16.0 0.0.20260723T184607-160000.1.1
opensuse advisories openSUSE-SU-2026:21483-1
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 7 mo ago
Exploit prediction
0.23% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N |
| GitHub | 3.1 | 4.3 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost/server/v8 | <8.0.0-20260107144005-c7f6efdfb035 |
8.0.0-20260107144005-c7f6efdfb035 |
| go | github.com/mattermost/mattermost-server | <5.3.2-0.20260107144005-c7f6efdfb035 >=10.11.0-rc1, <10.11.11 >=11.2.0-rc1, <11.2.3 >=11.3.0-rc1, <11.3.1 >=10.11.0-rc1+incompatible, <10.11.11+incompatible >=11.2.0-rc1+incompatible, <11.2.3+incompatible >=11.3.0-rc1+incompatible, <11.3.1+incompatible |
5.3.2-0.20260107144005-c7f6efdfb035 10.11.11 11.2.3 11.3.1 10.11.11+incompatible 11.2.3+incompatible 11.3.1+incompatible |
| go | github.com/mattermost/mattermost-server/v5 | all versions |
no fix listed |
| go | github.com/mattermost/mattermost-server/v6 | all versions |
no fix listed |
Affected products
- Mattermost Mattermost
Classification
- Weakness
-
- CWE-863 Incorrect Authorization
References
Sources
- CVE List CVE-2026-4265
- GitHub Advisory GHSA-xpvf-6qcc-9jqc
- NVD CVE-2026-4265
- OSV GO-2026-4749
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