CVE Intelligence
Medium Access control

CVE-2025-9081 — IDOR in board file download allows any user to download any file by UUID

Mattermost versions 10.5.x <= 10.5.8, 9.11.x <= 9.11.17 fail to properly validate access controls which allows any authenticated user to download sensitive files via board file download endpoint using UUID enumeration

Published Sep 19, 2025 · Updated Oct 19, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Mattermost

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.3% (30-day exploitation probability)+3
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.28%
ahead of 19% of scored CVEs · Oct 19, 2026
Affects
Mattermost
Mattermost and 4 more
CVSS base
6.5
Medium · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Go Github.com/mattermost/mattermost/server/v8: fixed in version 8.0.0-20250721095935-11c36f4d1e44 — github.com (GitHub Security Advisories)
  • Go Github.com/mattermost/mattermost-server: fixed in version 10.5.9 — github.com (GitHub Security Advisories)
  • Go Github.com/mattermost/mattermost-server: fixed in version 9.11.18 — github.com (GitHub Security Advisories)
  • Go Github.com/mattermost/mattermost-plugin-boards: fixed in version 0.0.0-20250716054606-3f3e3becfe1d — github.com (GitHub Security Advisories)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Mattermost Mattermost, Mattermost Mattermost Server, Go Github.com/mattermost/mattermost-plugin-boards…).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Search available logs for exploit probes matching the vulnerability class (access control), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Mattermost Mattermost ≥ 10.5.0 and ≤ 10.5.8≥ 9.11.0 and ≤ 9.11.17 Vulnerable CVE Program (cve.org) e CISA ADP
Mattermost Mattermost Server ≥ 9.11.0 and < 9.11.17≥ 10.5.0 and < 10.5.9 Vulnerable NIST National Vulnerability Database
Go Github.com/mattermost/mattermost-plugin-boards < 0.0.0-20250716054606-3f3e3becfe1d Vulnerable GitHub Security Advisories
Go Github.com/mattermost/mattermost-server ≥ 10.5.0-rc1 and < 10.5.9≥ 9.11.0-rc1 and < 9.11.18 Vulnerable GitHub Security Advisories
Go Github.com/mattermost/mattermost/server/v8 < 8.0.0-20250721095935-11c36f4d1e44 Vulnerable GitHub Security Advisories

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.5 CVSS 3.1 Medium 2.8 3.6 nvd@nist.gov via NIST National Vulnerability Database
3.1 CVSS 3.1 Low 1.6 1.4 responsibledisclosure@mattermost.com via NIST National Vulnerability Database
3.1 CVSS 3.1 Low — — GitHub, Inc. via GitHub Security Advisories
3.1 CVSS 3.1 Low — — Mattermost via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N (score shown at the top: nvd@nist.gov)
Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 6.5 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-639 · Authorization Bypass Through User-Controlled Key (IDOR)

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Audit administrative actions and access to resources outside each user’s normal pattern.
web/proxy/WAF logsnetwork IDS/IPSauthentication logsapplication logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • Fix documented
    Oct 19, 2026 · GitHub Security Advisories
  • Affected products added · go/github.com/mattermost/mattermost-plugin-boards, go/github.com/mattermost/mattermost/server/v8, go/github.com/mattermo
    Oct 19, 2026 · GitHub Security Advisories
  • Affected products added · mattermost/mattermost
    Oct 19, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 19, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 19, 2026
  • Affected products added · mattermost/mattermost server
    Oct 19, 2026 · NIST National Vulnerability Database
  • CVSS changed · 6.5
    Oct 19, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 19, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 19, 2026 · Alertas do Telegram
  • 2025
  • CVE published
    Sep 19, 2025 · Mattermost

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 19, 2026 – Oct 19, 2026
  • 1× Official description updated · Oct 19, 2026 – Oct 19, 2026

References

6 on the record

Elsewhere on this site

Mattermost
every CVE for this vendor
Access control
same class
CWE-639
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-19621 Mattermost leaks interactive-message integration secrets to non-admin users via post-deletion events and thread reads 4d
  • CVE-2026-18799 Mattermost Server fails to restrict Slack import account binding, allowing team admins to forge posts as existing users 4d
  • CVE-2026-19076 Mattermost fails to reject OAuth application sessions in account type switch, allowing account takeover via bearer token 4d
  • CVE-2026-19600 Mattermost logs plaintext authentication tokens in debug-level server logs on failed auth attempts 4d
  • CVE-2026-16251 Mattermost local image proxy allows server memory exhaustion via unbounded image response buffering 4d
  • CVE-2026-16453 Mattermost SAML RelayState forgery allows unauthorized team membership 4d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-9081 is "IDOR in board file download allows any user to download any file by UUID", rated Medium. It affects Mattermost (Mattermost); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.5 describes technical severity. EPSS 0.28% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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