CVE-2018-6406
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 · uneditedThe function ParseVP9SuperFrameIndex in common/libwebm_util.cc in libwebm through 2018-01-30 does not validate the child_frame_length data obtained from a .webm file, which allows remote attackers to cause an information leak or a denial of service (heap-based buffer over-read and later out-of-bounds write), or possibly have unspecified other impact.
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 confidenceThe ParseVP9SuperFrameIndex function in libwebm's common/libwebm_util.cc fails to validate child_frame_length values obtained from WebM files before using them in memory operations. This allows attackers to trigger heap-based buffer over-reads via crafted .webm files, leading to information disclosure or out-of-bounds write operations causing denial of service or potentially other impact.
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<= 2018-01-30CVSS 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
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/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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Locate the libwebm library or source code in your environmentSearch for files named libwebm, libwebm_util.cc, or the shared library (libwebm.so, libwebm.dylib, or libwebm.lib) commonly installed under /usr/lib, /usr/local/lib, or within application bundlesAffected if The library or source code is present and version cannot be determined or is dated 2018-01-30 or earlier
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Determine the installed version of libwebmCheck the version information in the library file metadata, or if building from source, inspect the source tree creation date or version tags in the repository (the vulnerability exists in commits up to and including 2018-01-30)Affected if The version is dated on or before 2018-01-30, or the source code contains the ParseVP9SuperFrameIndex function in common/libwebm_util.cc without the validated fix
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Verify if VP9 video decoding or WebM parsing is enabledCheck your application's configuration or build settings for flags that enable VP9 codec support or WebM container parsing (such as --enable-vp9, WebM demuxer, or libwebm linkage in the build)Affected if VP9 decoding or WebM container parsing is enabled and the application processes untrusted .webm files
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Inspect the ParseVP9SuperFrameIndex function for the vulnerabilityIf you have access to the source code, examine common/libwebm_util.cc and look for the ParseVP9SuperFrameIndex function - verify whether child_frame_length values are validated before use in memcpy, memset, or similar memory operationsAffected if The function lacks bounds checking on child_frame_length before performing memory operations, or uses these values directly without validation
Your environment is affected if libwebm version 2018-01-30 or earlier is installed and your application processes VP9-encoded WebM files with the vulnerable ParseVP9SuperFrameIndex function present.
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 dataUpdate libwebm to a version with the vulnerability patched, or implement application-layer input validation to reject WebM files containing malformed superframe index data with invalid child_frame_length values.
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 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 $3,984.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-6406 — 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-2018-6406 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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- Version or environment caveats, and links to real fixes
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