Ubuntu LinuxOperating system · Canonical
CVE-2016-4008
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 _asn1_extract_der_octet function in lib/decoding.c in GNU Libtasn1 before 4.8, when used without the ASN1_DECODE_FLAG_STRICT_DER flag, allows remote attackers to cause a denial of service (infinite recursion) via a crafted certificate.
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 _asn1_extract_der_octet function in lib/decoding.c of GNU Libtasn1 before version 4.8 contains an infinite recursion vulnerability. When processing ASN.1 encoded certificates without the ASN1_DECODE_FLAG_STRICT_DER flag enabled, specially crafted malicious certificates can trigger unbounded recursion, causing a denial of service through stack exhaustion.
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
FedoraOperating system
= 22= 23= 24= 13.2<= 4.7CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.0/AV:N/AC:H/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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Check installed libtasn1 versionRun 'dpkg -l libtasn1-6' on Debian/Ubuntu, 'rpm -q libtasn1' on RHEL/Fedora, or 'zypper se libtasn1' on openSUSEAffected if Version is 4.7 or lower, or for Ubuntu 12.04/14.04/15.10/16.04, Fedora 22/23/24, openSUSE 13.2 any packaged version
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Identify applications using libtasn1Search for binaries or libraries that link against libtasn1 using 'ldd' or 'objdump -p' on suspected binaries, or check application dependenciesAffected if Any application links to libtasn1 and processes ASN.1 certificates without using ASN1_DECODE_FLAG_STRICT_DER
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Check for strict DER flag usage in codeReview application source code or configuration for calls to asn1_decode_der, asn1_read_node, or similar decoding functions and verify whether ASN1_DECODE_FLAG_STRICT_DER is passed as a flag parameterAffected if Applications call decoding functions without the ASN1_DECODE_FLAG_STRICT_DER flag enabled
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Verify libtasn1 library file presenceLocate the library with 'find /usr -name "libtasn1*" -type f' or check /usr/lib/ directory contentsAffected if libtasn1 library file exists and is from an affected version
Environment is affected if libtasn1 version 4.7 or lower is installed AND applications using it do not enable the ASN1_DECODE_FLAG_STRICT_DER flag when decoding ASN.1 certificates.
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 GNU Libtasn1 version 4.8 or later. Alternatively, if upgrading is not feasible, ensure ASN1_DECODE_FLAG_STRICT_DER flag is used when calling the affected decoding functions.
Fix this in Ubuntu Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation1.0 h
- Testing4.0 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 $2,464.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-4008 — 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-2016-4008 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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