Insufficient Authorization On Unlinked Channel Files
Mattermost versions 9.10.x <= 9.10.1, 9.9.x <= 9.9.2, 9.5.x <= 9.5.8 fail to limit access to channels files that have not been linked to a post which allows an attacker to view them in channels that they are a member of.
- Published
- Sep 26, 2024
- Updated
- Jun 17, 2026
- EPSS
- 0.3% · 16th percentile
- CWE
- CWE-863
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Report tools
Action score
17
Monitor
Low priority for now.
- CVSS
- 17 / 40 · 4.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · Mattermost
- 4.3
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| mattermost | mattermost server | cpe:2.3:a:mattermost:mattermost_server |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- mattermost mattermost server9.5.0 and later · before 9.5.9
- mattermost mattermost server9.9.0 and later · before 9.9.3
- mattermost mattermost server9.10.0 and later · before 9.10.2
Versions reported by the vendor
Affected version ranges reported by the assigning authority (Mattermost). Independent of NVD's CPE analysis and usually ahead of it.
Mattermost Mattermost
- 9.11.0, 9.10.2, 9.9.3, 9.5.9not affected
- 9.10.0 and later · up to and including 9.10.1affected · semver
- 9.9.0 and later · up to and including 9.9.2affected · semver
- 9.5.0 and later · up to and including 9.5.8affected · semver
Same product
mattermost: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-4858Path traversal in integration action URL leading to arbitrary API execution via system admin’s auth token.39Monitor
- CVE-2025-12421Account Takeover via Code Exchange Endpoint39Monitor
- CVE-2025-12419Account takeover on OAuth/OpenID-enabled servers39Monitor
- CVE-2025-4981Path Traversal Leading to RCE by Any Authenticated Mattermost User39Monitor
- CVE-2023-6458Client side path traversal due to lack of route parameters validation39Monitor
- CVE-2017-18920An issue was discovered in Mattermost Server before 3.6.2.39Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
No fix version is recorded for this entry. Check the references for vendor advisories.
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- Lorenzo Gallegosfinder
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
- CVE-2025-25274176 days apartUnauthorized Command Execution in Archived Channels35Monitor
- CVE-2023-2515503 days apartPrivilege escalation to system admin via personal access tokens35Monitor
- CVE-2023-3590437 days apartDeleted attachments in Boards remain accessible30Monitor
- CVE-2025-30179176 days apartMFA Enforcement Bypass in Search APIs26Monitor
- CVE-2026-2462536 days apartAdmin RCE via Malicious Plugin Upload on CI Test Instances26Monitor
- CVE-2025-46702277 days apartMattermost Playbooks allows privilege escalation through improper access control in playbook run participant management21Monitor
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- low · data can be read
- Integrity
- none
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- Low
- Integrity impact
- None
- Availability impact
- None
Weakness class (CWE)
CWE-863 · Incorrect AuthorizationCVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.