CVE-2017-10687
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 · uneditedIn LibSass 3.4.5, there is a heap-based buffer over-read in the function json_mkstream() in sass_context.cpp. A crafted input will lead to a remote denial of service attack.
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 confidenceLibSass 3.4.5 contains a heap-based buffer over-read vulnerability in the json_mkstream() function in sass_context.cpp. When processing crafted input, the function reads beyond allocated buffer boundaries, causing memory access violations that lead to denial of service. This is a memory safety issue in C++ code that can be triggered remotely via malicious Sass input.
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= 3.4.5CVSS 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:3.0/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 LibSass version in useRun 'libsass --version' or check the package version via your package manager (npm list libsass, gem list libsass, pip show libsass, or equivalent depending on your integration method)Affected if The installed version is exactly 3.4.5
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Determine if JSON output is being generatedInspect your build configuration or CI/CD pipeline for flags that trigger JSON output from LibSass, such as --json, --style=json, or programmatic use of Sass::JsonExecutor or similar JSON-related output optionsAffected if JSON output is enabled and LibSass 3.4.5 is processing Sass files through the json_mkstream() code path
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Identify processes and input files feeding LibSassReview application logs or instrument the build process to capture which Sass files are being processed by LibSass 3.4.5 and whether the json_mkstream() function is invokedAffected if LibSass 3.4.5 is actively compiling Sass input and producing JSON-formatted output
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Check for automated or remote Sass compilationAudit any web endpoints, APIs, or automated systems that accept Sass input and pass it to LibSass 3.4.5 for compilation, especially those that generate JSON outputAffected if External or untrusted Sass input can reach LibSass 3.4.5 with JSON output enabled
You are affected if LibSass version 3.4.5 is installed and the json_mkstream() function is invoked to process Sass input into JSON output.
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 dataUpgrade LibSass to version 3.5.0 or later where the vulnerability is patched. If immediate upgrading is not feasible, implement strict input validation on Sass files before processing and consider rate limiting or sandboxing to reduce exposure.
- Consultation3.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-10687 — 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-2017-10687 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
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