CVE-2016-7439
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 C software implementation of RSA in wolfSSL (formerly CyaSSL) before 3.9.10 makes it easier for local users to discover RSA keys by leveraging cache-bank hit differences.
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 C software implementation of RSA in wolfSSL (formerly CyaSSL) before version 3.9.10 contains a timing side-channel vulnerability. Local attackers can exploit cache-bank hit differences to potentially discover RSA private keys through statistical analysis of timing variations during cryptographic operations.
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<= 3.9.8CVSS 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
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/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 if wolfSSL is installedSearch for wolfSSL libraries or headers on the system. Common paths include /usr/lib/libwolfssl.so, /usr/local/lib/libwolfssl.so, or check for wolfssl/wolfcrypt headers in include directories. Also check package managers for installed wolfssl packages.Affected if wolfSSL library is present on the system
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Determine the installed wolfSSL versionRun 'wolfssl version' if the command-line tool is available, or inspect the library binary with 'strings libwolfssl.so | grep -i version' or check the shared library version with 'ldd' or 'objdump -p'. For source builds, check the version defined in wolfssl/version.h.Affected if The version number returned is 3.9.8 or earlier, or cannot be determined to be 3.9.10 or later
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Check if RSA cryptographic operations are in useReview application code, configuration files, or runtime logs for usage of RSA encryption, decryption, signing, or verification functions (such as wc_RsaEncrypt, wc_RsaDecrypt, wc_RsaSign, wc_RsaVerify). Inspect any TLS/SSL configuration that specifies RSA key exchange or RSA certificates.Affected if The application or service performs RSA operations using the wolfSSL library
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Verify the RSA implementation is software-basedConfirm that the wolfSSL build is using the native C software implementation for RSA rather than a hardware-backed or alternative cryptographic library. Check build configuration files, configure flags, or runtime settings for NO_HW_RSA or similar options that indicate software-only RSA.Affected if wolfSSL is compiled with the standard C RSA implementation (default configuration) and no hardware acceleration is in use
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Check for exposure to local attackersAssess whether unprivileged local users or processes have the ability to observe timing variations during cryptographic operations, or whether the system runs wolfSSL-based services that handle sensitive RSA private keys locally.Affected if Local users can potentially measure timing differences during RSA operations or the system processes sensitive RSA keys locally
A system is affected if it runs wolfSSL version 3.9.8 or earlier and performs RSA operations using the software-based RSA implementation, allowing local attackers with timing measurement capabilities to potentially extract private keys.
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 wolfSSL to version 3.9.10 or later which contains the fix for this timing side-channel vulnerability. If upgrading is not immediately feasible, review whether RSA operations handling sensitive keys can be isolated or moved to updated cryptographic libraries.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-7439 — 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-2016-7439 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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- 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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