Security readout for executives and security teams
Plain-English summary
CVE-2021-47476 is a Linux kernel driver flaw that can let a malicious or malformed USB device crash an affected system. It concerns the Comedi ni_usb6501 driver. The business risk is mainly downtime where untrusted physical USB devices can be connected.
Executive priority
Treat as normal-priority kernel hygiene, with faster action for systems where users or visitors can attach USB hardware. It is not currently supported as internet-exploitable or actively exploited by the provided evidence.
Technical view
The ni_usb6501 Comedi driver lacked endpoint max-packet size checks during probe. Small or malformed USB descriptors could trigger zero-size pointer dereferences or overflowed transfer buffers in ni6501_port_command() and ni6501_counter_command(), causing high availability impact.
Likely exposure
Exposure is most likely on Linux systems with the ni_usb6501 Comedi USB driver present and reachable by physical USB attachment. Locked-down servers without accessible USB ports are less exposed.
Exploitation context
The CVSS vector requires physical access. The provided sources do not show active exploitation, and KEV is false. Evidence supports crash or denial-of-service risk, not confidentiality or integrity compromise.
Researcher notes
The issue is CWE-476 and availability-focused. The root cause is missing sanity checks on USB endpoint-sized transfer buffers during probe, affecting command paths when descriptors report smaller max-packet sizes than expected.
Mitigation direction
- Apply Linux kernel updates containing the referenced stable fixes.
- Follow distribution vendor advisories for exact fixed kernel packages.
- Disable or avoid loading ni_usb6501 if the hardware is not needed.
- Restrict physical USB access on exposed workstations, kiosks, and lab systems.
Validation and detection
- Inventory Linux systems for affected kernel versions and Comedi driver use.
- Check whether the ni_usb6501 module is present or loaded.
- Compare deployed kernels against vendor fixed package guidance or stable commit backports.
- Review physical USB access controls for systems where the driver is enabled.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-476: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-47476 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.6 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
SSVC decision data
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H0.93.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
4.6MediumVector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/58478143771b20ab219937b1c30a706590a59224CVE reference, Linux
- https://git.kernel.org/stable/c/aa39738423503825625853b643b9e99d11c23816CVE reference, Linux
- https://git.kernel.org/stable/c/df7b1238f3b599a0b9284249772cdfd1ea83a632CVE reference, Linux
- https://git.kernel.org/stable/c/bc51111bf6e8e7b6cc94b133e4c291273a16acd1CVE reference, Linux
- https://git.kernel.org/stable/c/b0156b7c9649d8f55a2ce3d3258509f1b2a181c3CVE reference, Linux
- https://git.kernel.org/stable/c/ef143dc0c3defe56730ecd3a9de7b3e1d7e557c1CVE reference, Linux
- https://git.kernel.org/stable/c/4a9d43cb5d5f39fa39fc1da438517004cc95f7eaCVE reference, Linux
- https://git.kernel.org/stable/c/d6a727a681a39ae4f73081a9bedb45d14f95bdd1CVE reference, Linux
- https://git.kernel.org/stable/c/907767da8f3a925b060c740e0b5c92ea7dbec440CVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
NULL Pointer Dereference
NULL Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.