CVE-2025-9078Network attack vector

Unauthorized post access via colliding link-cache keys

Published Sep 15, 2025 · Updated Sep 15, 2025

Use of a weak hash in Mattermost Server allows remote authenticated users to access unauthorized posts through crafted link previews. The link-metadata cache indexes entries with an FNV-1 hash of a URL and timestamp, then returns a matching-key entry without confirming that its stored URL matches the requested URL. A logged-in user who supplies a colliding URL can receive cached permalink metadata for another post or substitute attacker-controlled preview metadata; no service interruption or direct post modification is reported.

CVSS severity4.3
Medium
EPSS probability0.15%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use of a weak hash in Mattermost Server allows remote authenticated users to access unauthorized posts through crafted link previews. The link-metadata cache indexes entries with an FNV-1 hash of a URL and timestamp, then returns a matching-key entry without confirming that its stored URL matches the requested URL. A logged-in user who supplies a colliding URL can receive cached permalink metadata for another post or substitute attacker-controlled preview metadata; no service interruption or direct post modification is reported.

The record

CVE
CVE-2025-9078
Published
Sep 15, 2025
Updated
Sep 15, 2025
Vendor
Mattermost
Product
Mattermost
Classifications
CWE-328, T1213.005
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 15, 2025CVE publishedPublication date reported by the CVE source.
  2. Sep 15, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.10.0 <=10.10.1
  2. Affected versionversion=10.5.0 <=10.5.8
  3. Affected versionversion=10.8.0 <=10.8.3
  4. Affected versionversion=10.9.0 <=10.9.3
  5. Affected versionversion=9.11.0 <=9.11.17

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Mattermost · Mattermostversion=10.10.0 <=10.10.1; version=10.5.0 <=10.5.8; version=10.8.0 <=10.8.3; version=10.9.0 <=10.9.3; version=9.11.0 <=9.11.17

Published CVSS scores

4.3Mattermost, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-328Use of Weak Hash
T1213.005Data from Information Repositories: Messaging Applications

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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