Security readout for executives and security teams
Plain-English summary
This Linux kernel flaw can hang a machine when kernel tracing recurses into trace_clock_global() and deadlocks. The business impact is availability, not data theft. Evidence points to local, low-privilege exposure and no cited active exploitation.
Executive priority
Treat as a normal-priority availability fix for Linux fleets, with faster action on multi-user or operationally critical hosts. It does not justify emergency response unless vulnerable systems are stability-sensitive or local users can exercise tracing paths.
Technical view
trace_clock_global() took a spin lock while tracing. A permitted single recursion could re-enter ring_buffer_lock_reserve(), call trace_clock_global() again, and block on the same lock, causing a deadlock. The kernel fix changes the update path to avoid blocking by using a trylock.
Likely exposure
Linux systems running affected kernel builds are the relevant exposure. Risk is highest where local users or operational tooling can trigger kernel tracing paths, including function graph tracing during suspend or resume testing. Network-only exposure is not supported by the provided CVSS vector.
Exploitation context
The CVSS vector is local, low complexity, low privileges, no user interaction, and high availability impact. The source bundle marks KEV as false and provides no evidence of public exploitation or in-the-wild attacks.
Researcher notes
The issue is CWE-400 resource management through a non-blocking requirement violation in tracing. The public record is clear on root cause and fix direction, but the supplied affected-version data is commit/version oriented and should be reconciled through distro advisories.
Mitigation direction
- Update to a vendor-supported Linux kernel containing the referenced stable fixes.
- Check Linux distribution advisories for the exact fixed package version.
- Prioritize shared systems where local users can access tracing features.
- Avoid relying on custom workarounds unless vendor guidance confirms them.
Validation and detection
- Inventory Linux kernel versions across servers, workstations, and appliances.
- Compare installed kernels against vendor advisories and referenced stable commits.
- Review whether tracing or function graph tracing is enabled or delegated to users.
- Confirm patched systems no longer map to affected kernel records.
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-400: 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-2021-46939 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
- 5.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/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:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H1.83.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
5.5MediumVector: CVSS:3.1/AV:L/AC:L/PR:L/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/91ca6f6a91f679c8645d7f3307e03ce86ad518c4CVE reference, Linux
- https://git.kernel.org/stable/c/859b47a43f5a0e5b9a92b621dc6ceaad39fb5c8bCVE reference, Linux
- https://git.kernel.org/stable/c/1fca00920327be96f3318224f502e4d5460f9545CVE reference, Linux
- https://git.kernel.org/stable/c/d43d56dbf452ccecc1ec735cd4b6840118005d7cCVE reference, Linux
- https://git.kernel.org/stable/c/c64da3294a7d59a4bf6874c664c13be892f15f44CVE reference, Linux
- https://git.kernel.org/stable/c/a33614d52e97fc8077eb0b292189ca7d964cc534CVE reference, Linux
- https://git.kernel.org/stable/c/6e2418576228eeb12e7ba82edb8f9500623942ffCVE reference, Linux
- https://git.kernel.org/stable/c/2a1bd74b8186d7938bf004f5603f25b84785f63eCVE reference, Linux
- https://git.kernel.org/stable/c/aafe104aa9096827a429bc1358f8260ee565b7ccCVE 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.
Uncontrolled Resource Consumption
Uncontrolled Resource Consumption represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.