FedoraOperating system · Fedoraproject
CVE-2021-28484
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 · uneditedAn issue was discovered in the /api/connector endpoint handler in Yubico yubihsm-connector before 3.0.1 (in YubiHSM SDK before 2021.04). The handler did not validate the length of the request, which can lead to a state where yubihsm-connector becomes stuck in a loop waiting for the YubiHSM to send it data, preventing any further operations until the yubihsm-connector is restarted. An attacker can send 0, 1, or 2 bytes to trigger this.
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 /api/connector endpoint handler in yubihsm-connector lacks request length validation, allowing an attacker to send 0, 1, or 2 bytes which causes the connector to enter an infinite loop waiting for data from the YubiHSM device, rendering it unresponsive until restarted.
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
FedoraOperating system
= 34< 3.0.1CVSS 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:3.1/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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Check if yubihsm-connector is installedOn Fedora 34, run: rpm -qa | grep -i yubihsm or dnf list installed yubihsm-connectorAffected if No yubihsm-connector package is found, the system is not affected by this CVE
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Identify the installed yubihsm-connector versionRun: rpm -q yubihsm-connector or check the SDK version with yubihsm-connector --version if availableAffected if The version returned is less than 3.0.1 (or the SDK version is earlier than 2021.04)
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Verify the /api/connector endpoint is exposedCheck the connector configuration file (typically in /etc/yubihsm-connector or the deployed configuration) for the HTTP listener bind address and port, then confirm network accessibilityAffected if The connector is listening on an accessible network interface and the /api/connector endpoint is reachable
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Test connector responsiveness via the APISend a minimal request (0, 1, or 2 bytes) to the /api/connector endpoint using: echo -n '' | nc <host> <port> or curl with limited bytes, and observe if the connector becomes unresponsiveAffected if The connector hangs or becomes unresponsive after receiving a short malformed request, indicating the vulnerability is present
A system is affected if yubihsm-connector version less than 3.0.1 is installed and the /api/connector endpoint is network-accessible, as the missing request length validation will cause infinite loops on malformed 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 data3.0.1
Upgrade to yubihsm-connector version 3.0.1 (YubiHSM SDK 2021.04 or later) which implements proper request length validation at the API endpoint handler.
Fix this in Fedora
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,096.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-28484 — 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-2021-28484 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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