Security readout for executives and security teams
Plain-English summary
This is a Linux kernel bug in block tracing. A local actor could trigger a race where tracing data is freed while still being used, potentially crashing the kernel or exposing memory. The source bundle does not show active exploitation or a standalone vendor advisory beyond kernel stable fixes.
Executive priority
Treat as a moderate kernel maintenance issue. It is not documented as actively exploited, but kernel memory safety bugs matter on shared Linux systems. Prioritize routine patching, with faster action for multi-user or high-value hosts.
Technical view
CVE-2021-47375 is a CWE-416 use-after-free in Linux blktrace. Disabling tracing through sysfs can free blk_trace resources while __blk_add_trace still iterates running_trace_list and reaches relay_reserve through stale state. The stated fix removes blk_trace from the running list before blk_trace_free when tracing is running.
Likely exposure
Exposure is mainly Linux systems running affected kernel versions with blktrace/block tracing available. Risk is higher on multi-user systems, shared compute, and hosts where local users or workloads can reach block device tracing paths. Practical reachability may depend on device and sysfs permissions.
Exploitation context
The provided CVSS is 6.2 with local attack vector, low complexity, no user interaction, and high confidentiality impact. KEV is false, and the bundle provides no evidence of exploitation in the wild. The included reproduction detail indicates local kernel interaction, not remote exploitation.
Researcher notes
The evidence supports a race in blktrace teardown versus trace emission. The source describes stale blk_trace access after sysfs removal and a fix ordering change around running_trace_list and blk_trace_free. Do not assume remote reachability or weaponized exploit availability from the provided sources.
Mitigation direction
- Update to a kernel build containing the referenced stable fixes.
- Check distribution advisories for backported CVE-2021-47375 fixes.
- Restrict local access to block devices and tracing interfaces where possible.
- Review shared or multi-tenant Linux hosts first.
- Avoid enabling blktrace unless operationally required.
Validation and detection
- Inventory Linux kernel versions across affected server and workstation fleets.
- Confirm vendor kernel changelogs mention CVE-2021-47375 or the stable fix commits.
- Check whether blktrace and /sys/block/*/trace are available on sensitive systems.
- Prioritize validation on multi-user, CI, build, and shared compute hosts.
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-416: 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-2021-47375 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
- 6.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N2.53.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
6.2MediumVector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
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/488da313edf3abea7f7733efe011c96b23740ab5CVE reference, Linux
- https://git.kernel.org/stable/c/dacfd5e4d1142bfb3809aab3634a375f6f373269CVE reference, Linux
- https://git.kernel.org/stable/c/d56171d9360c0170c5c5f8f7e2362a2e999eca40CVE reference, Linux
- https://git.kernel.org/stable/c/677e362ba807f3aafe6f405c07e0b37244da5222CVE reference, Linux
- https://git.kernel.org/stable/c/ebb8d26d93c3ec3c7576c52a8373a2309423c069CVE reference, Linux
- https://git.kernel.org/stable/c/3815fe7371d2411ce164281cef40d9fc7b323deeCVE reference, Linux
- https://git.kernel.org/stable/c/a5f8e86192612d0183047448d8bbe7918b3f1a26CVE reference, Linux
- https://git.kernel.org/stable/c/5afedf670caf30a2b5a52da96eb7eac7dee6a9c9CVE 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.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.