CVE-2016-6879
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 X509_Certificate::allowed_usage function in botan 1.11.x before 1.11.31 might allow attackers to have unspecified impact by leveraging a call with more than one Key_Usage set in the enum value.
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 · moderate confidenceIn Botan 1.11.x before 1.11.31, the X509_Certificate::allowed_usage function contains a logic flaw when handling Key_Usage extensions that have more than one usage flag set in the enum value. This likely causes incorrect bitmask comparisons when validating certificate usage constraints, potentially allowing certificates to be accepted for unauthorized purposes.
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= 1.11.0= 1.11.1= 1.11.2= 1.11.3= 1.11.4= 1.11.5= 1.11.6= 1.11.7= 1.11.8= 1.11.9= 1.11.10= 1.11.11CVSS 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
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
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 Botan library installation and versionLocate the Botan library in your environment and determine its version number. Common methods include checking library files, build artifacts, package manager listings, or inspecting version headers in the Botan source code if compiled locally.Affected if The installed version is 1.11.x and falls within the range 1.11.0 through 1.11.11 (or any version before 1.11.31)
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Locate X509_Certificate::allowed_usage usage in codeSearch your codebase for calls to the X509_Certificate::allowed_usage method or references to X509 certificate validation logic that checks Key_Usage extensions.Affected if Your application uses X509_Certificate::allowed_usage to validate certificate Key_Usage extensions
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Determine if Key_Usage extensions with multiple flags are processedReview your certificate validation flow to identify whether certificates with Key_Usage extensions containing more than one usage flag (such as digitalSignature + keyEncipherment) are being validated against usage constraints.Affected if Your environment processes certificates that have Key_Usage extensions with multiple bits set in the extension value
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Verify bitmask comparison behavior in certificate validationIf possible, inspect the Botan library source code for the X509_Certificate::allowed_usage implementation to confirm whether the bitmask comparison logic uses a single-bit test (like (usage & flag) == flag) rather than a proper multi-bit test.Affected if The installed Botan library contains the flawed bitmask comparison logic in X509_Certificate::allowed_usage
You are affected if your environment uses Botan TLS library versions 1.11.0 through 1.11.11 (or any version before 1.11.31) and performs X509 certificate validation with Key_Usage extensions that contain multiple usage flags.
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 Botan TLS library to version 1.11.31 or later to obtain the fixed implementation of X509_Certificate::allowed_usage.
- Consultation2.0 h
- Implementation4.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-6879 — 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-2016-6879 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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