CVE-2025-47712
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 · uneditedA flaw exists in the nbdkit "blocksize" filter that can be triggered by a specific type of client request. When a client requests block status information for a very large data range, exceeding a certain limit, it causes an internal error in the nbdkit, leading to a denial of service.
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 confidenceA flaw in nbdkit's 'blocksize' filter allows a client to trigger a denial of service by requesting block status information for a data range exceeding internal limits. The vulnerability stems from improper handling of oversized block status requests, causing an internal error that crashes the nbdkit service.
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 dataall versionsCVSS 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
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/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 nbdkit installation and versionRun 'nbdkit --version' or check your package manager for installed nbdkit package versionAffected if Any installed version of nbdkit is affected since all versions are vulnerable
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Determine if blocksize filter is loadedReview nbdkit configuration files (typically in /etc/nbdkit or /etc/cloudstack/nbd) and startup scripts for 'blocksize' filter presence in the filter chainAffected if Blocksize filter must be loaded and active for this vulnerability to be exploitable
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Check for exposed NBD service accessReview network configuration and firewall rules to determine if the NBD server port (typically 10809) is accessible to untrusted or internet-facing clientsAffected if If untrusted clients can reach the NBD service, they can send malicious block status requests
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Inspect logs for crash indicatorsCheck nbdkit service logs (journalctl -u nbdkit or /var/log/nbdkit.log) for 'blocksize' filter errors or unexpected service crashes around block status operationsAffected if Recent crashes or errors related to block status requests indicate active exploitation or trigger conditions
You are affected if nbdkit with the blocksize filter is running and accessible to untrusted clients, and you observe crash behavior from oversized block status requests.
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 dataApply any available patches from nbdkit maintainers. As a defensive measure, consider restricting untrusted client access to the NBD server or implementing rate limiting on block status requests.
- 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-2025-47712 — 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-2025-47712 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
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