Ubuntu LinuxOperating system · Canonical
CVE-2016-4574
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 · uneditedOff-by-one error in the append_utf8_value function in the DN decoder (dn.c) in Libksba before 1.3.4 allows remote attackers to cause a denial of service (out-of-bounds read) via invalid utf-8 encoded data. NOTE: this vulnerability exists because of an incomplete fix for CVE-2016-4356.
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 confidenceOff-by-one error in append_utf8_value function in dn.c in Libksba before 1.3.4 allows out-of-bounds read via invalid UTF-8 encoded data in the Distinguished Name (DN) decoder. This is an incomplete fix for CVE-2016-4356, where the initial patch did not fully address the boundary condition. Remote attackers can trigger this by presenting malformed X.509 certificate data with specially crafted UTF-8 sequences.
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
Ubuntu LinuxOperating system
= 12.04= 14.04= 15.10= 16.04<= 1.3.3= 42.1= 13.2CVSS 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 if Libksba is installedRun 'dpkg -l | grep libksba' on Debian/Ubuntu, or 'rpm -qa | grep -i ksba' on RHEL/SUSE, or 'ls /usr/lib*/libksba*' to locate the library fileAffected if Libksba is not installed or no library file is found - the vulnerability does not apply
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Check the installed Libksba versionRun 'ksba-config --version' if available, or check the library file version with 'objdump -p /usr/lib*/libksba.so.8 | grep Version' or 'dpkg -s libksba'Affected if Version is 1.3.3 or lower, or the package version indicates anything before 1.3.4 - the system is potentially affected
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Identify applications using LibksbaRun 'ldd /path/to/binary | grep ksba' on suspected binaries, or 'find /usr -name "*.so*" -exec ldd {} \; 2>/dev/null | grep -i ksba' to find linked binaries, or check GnuPG with 'gpg --version' and verify it links to libksbaAffected if Applications that parse X.509 certificates or handle DNs are linked against a vulnerable Libksba version - the flaw can be triggered
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Determine if certificate processing is in useReview logs or configuration for services accepting or verifying X.509 certificates (TLS/SSL services, S/MIME, code signing), or check for certificates in PEM/DER format being processedAffected if The environment processes X.509 certificates with UTF-8 encoded Subject/Issuer DNs - malformed certificates could trigger the out-of-bounds read
A system is affected if it runs Libksba version 1.3.3 or earlier AND processes X.509 certificates containing specially crafted UTF-8 sequences in Distinguished Names.
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 to Libksba version 1.3.4 or later to obtain the complete fix. Audit all applications and services that link against Libksba to ensure they are rebuilt against the updated library.
Fix this in Ubuntu Linux
Scoped from the published advisory
- 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-2016-4574 — 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-2016-4574 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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