CVE-2015-9548
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 Server before 1.2.0. It allows attackers to cause a denial of service (memory consumption) via a small compressed file that has a large size when uncompressed.
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 confidenceMattermost Server before 1.2.0 is vulnerable to a decompression bomb attack where a small compressed file expands to enormous size when uncompressed, exhausting server memory and causing denial of service. The server processes compressed files (likely attachments or imports) without enforcing limits on the uncompressed size ratio.
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< 1.2.0CVSS 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
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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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Identify Mattermost Server versionCheck the version displayed in the Mattermost UI footer, or query the server API endpoint /api/v1/system/status, or run 'mattermost version' from the command line if you have CLI access, or inspect the installed package/binary metadataAffected if The installed version is earlier than 1.2.0 (e.g., 1.1.x, 1.0.x)
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Determine if file attachments are enabledReview the Mattermost configuration file (config.json) for the 'FileSettings.EnableFileAttachments' setting, or check via the System Console under File SettingsAffected if File attachments are enabled (this is the default and likely setting for most installations)
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Check if compression is used for uploadsInspect whether the server accepts compressed file types (.zip, .gz, .tar, etc.) as attachments or via import features by reviewing allowed file extensions in configuration or testing with a compressed test fileAffected if Compressed file formats are accepted as uploads or imports without additional verification
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Verify decompression size limits existSearch configuration files and logs for any settings related to max decompression size, compression ratio limits, or 'max uncompressed size' - these may appear in config.json or as environment variablesAffected if No decompression size limits or ratio limits are configured, and compressed files can expand arbitrarily during processing
You are affected if your Mattermost Server version is below 1.2.0 and the server accepts compressed file uploads or imports without enforcing a maximum uncompressed size limit.
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.
From vendor data1.2.0
Upgrade to Mattermost Server 1.2.0 or later which should include decompression size limits. Additionally, implement application-layer limits on maximum uncompressed-to-compressed size ratios before processing any uploaded or imported compressed files.
- Consultation3.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,128.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2015-9548 — 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-2015-9548 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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
- No spam, self-promotion, credentials, or personal data