CVE-2019-20851
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedAn issue was discovered in Mattermost Mobile Apps before 1.26.0. An attacker can use directory traversal with the Video Preview feature to overwrite arbitrary files on a device.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA directory traversal vulnerability in the Video Preview feature of Mattermost Mobile Apps (versions before 1.26.0) allows attackers to use path traversal sequences (e.g., ../) to write files to arbitrary locations on the device filesystem, potentially overwriting system files or application data.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 1.26.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check the installed Mattermost Mobile Apps versionOpen the app store (Google Play Store or Apple App Store), go to Mattermost app page, and view the version information. Or on the device, go to Settings > Apps > Mattermost to see the installed version.Affected if The installed version is any version prior to 1.26.0 (e.g., 1.25.0, 1.24.0, etc.)
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Confirm Video Preview feature is accessibleIn the Mattermost mobile app, navigate to a channel that supports video sharing or preview functionality. The vulnerability exists in the Video Preview feature.Affected if The Video Preview feature is present and functional in the app, which is the case for all versions before 1.26.0 that include this feature.
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Check for file system write access via path traversalAttempt to understand if the app has permission to write files outside its sandbox. The vulnerability allows path traversal via ../ sequences in video preview file handling.Affected if The app can process video previews and has file system write permissions, which is the default behavior for versions before 1.26.0.
You are affected if the Mattermost Mobile Apps version installed on your device is below 1.26.0 and the Video Preview feature is accessible and enabled.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped1.26.0
Upgrade Mattermost Mobile Apps to version 1.26.0 or later, which contains the fix for the directory traversal vulnerability in the Video Preview feature.
1.26.0
- Open the App Store (iOS) or Google Play Store (Android) on your mobile device
- Search for "Mattermost" or locate the installed Mattermost app
- Tap Update to install version 1.26.0 or later
- Alternatively, download the latest Mattermost Mobile App directly from the official Mattermost website or trusted app distribution platform
- After updating, verify the app version in the app settings to confirm the fix is applied
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-20851 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2019-20851 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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