Security readout for executives and security teams
Plain-English summary
CVE-2021-47578 is a Linux kernel bug in the SCSI debug driver. A zero-size allocation can produce a special pointer that later leads to a null-pointer dereference during buffer copying. The clearest business impact is potential kernel instability or denial of service on systems where this debug driver is available and reachable.
Executive priority
Treat this as a kernel reliability issue with limited likely exposure. Prioritize patching in normal kernel maintenance, and escalate only for systems where scsi_debug is enabled or untrusted users can interact with SCSI generic interfaces.
Technical view
The flaw is in drivers/scsi/scsi_debug.c. kcalloc() with a zero size can return ZERO_SIZE_PTR, bypassing a later NULL check. The reported KASAN trace reaches sg_copy_buffer(), do_dout_fetch(), resp_verify(), and scsi_debug_queuecommand(). The kernel fix returns early before kcalloc() when the requested size is zero.
Likely exposure
Exposure appears limited to Linux systems using or allowing access to the scsi_debug driver. This is commonly a testing/debug component, so broad production exposure is less likely, but kernel builds and module policy determine real risk.
Exploitation context
The provided sources show a syzkaller-style KASAN crash trace and stable kernel fixes. They do not show active exploitation, weaponized exploit availability, remote attack paths, or CISA KEV listing.
Researcher notes
Evidence supports a null-pointer dereference triggered through scsi_debug code paths after a zero-size allocation. The source bundle does not provide CVSS, CWE, proof of exploitation, privilege requirements, or distribution-specific affected package ranges.
Mitigation direction
- Apply Linux kernel stable updates containing the referenced fixes.
- Check vendor kernel advisories for backported fixes in your distribution.
- Disable or restrict the scsi_debug module where it is not operationally required.
- Review module loading policy for debug or test-only kernel drivers.
Validation and detection
- Inventory kernels for affected Linux versions and vendor backport status.
- Check whether the scsi_debug module is present, loadable, or loaded.
- Confirm patched kernels include the referenced stable commits or equivalent backports.
- Review logs for kernel crashes involving scsi_debug, sg_copy_buffer, or resp_verify.
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.
CVE-2021-47578 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
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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
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/aa1f912712a109b6306746133de7e5343f016b26CVE reference, Linux
- https://git.kernel.org/stable/c/47d11d35203b0aa13533634e270fe2c3610e531bCVE reference, Linux
- https://git.kernel.org/stable/c/3344b58b53a76199dae48faa396e9fc37bf86992CVE 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.