CVE-2015-5276
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 std::random_device class in libstdc++ in the GNU Compiler Collection (aka GCC) before 4.9.4 does not properly handle short reads from blocking sources, which makes it easier for context-dependent attackers to predict the random values via unspecified vectors.
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 std::random_device class in libstdc++ (part of GCC before 4.9.4) fails to properly handle short reads from blocking entropy sources. When a blocking source returns less data than requested, the implementation does not correctly reseed or retry, leading to reduced entropy in the generated random values. This makes the random output more predictable, enabling context-dependent attackers to potentially deduce the sequence.
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< 4.9.4CVSS 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
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- None
- Availability
- None
AV:N/AC:L/Au:N/C:P/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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Check GCC versionRun 'gcc --version' or 'g++ --version' to determine the installed GCC compiler versionAffected if The version shown is earlier than 4.9.4 (for example, 4.9.3, 4.8.x, etc.)
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Identify std::random_device usageSearch source code for '#include <random>' and 'std::random_device' usage patterns using grep or a code search toolAffected if Code contains std::random_device instances that generate random values for any purpose
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Verify libstdc++ library versionLocate the libstdc++ library file (typically libstdc++.so on Linux) and query its version via 'strings' or check the package version if installed via a package managerAffected if The linked libstdc++ library corresponds to a GCC version earlier than 4.9.4
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Confirm blocking entropy source is in useOn Linux systems, std::random_device typically reads from /dev/urandom or /dev/random; verify which source is configured by examining the application behavior or documentationAffected if The application uses a blocking entropy source (such as /dev/random) that can return fewer bytes than requested, triggering the flawed retry logic
You are affected if your installed GCC version is earlier than 4.9.4 AND your code uses std::random_device with a blocking entropy source that can return partial reads.
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 data4.9.4
Upgrade GCC to version 4.9.4 or later to obtain the fixed libstdc++ library. Additionally, audit any code relying on std::random_device for security-critical purposes and consider using alternative CSPRNG implementations if the risk is unacceptable.
- Consultation4.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2015-5276 — 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-2015-5276 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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