Security readout for executives and security teams
Plain-English summary
This is a Linux kernel memory-safety bug in the scsi_debug driver, a SCSI testing/debug component. A malformed SCSI read-capacity request can make the kernel read past a small stack buffer. Business impact depends heavily on whether scsi_debug is present, loaded, and reachable by local users or test workloads.
Executive priority
Prioritize remediation on shared Linux systems, test infrastructure, and hosts exposing SCSI generic access to untrusted local users. For typical production servers without scsi_debug, urgency is lower but should still be tracked through normal kernel patching.
Technical view
resp_readcap16() treated an allocation length as signed int. A negative value could become a huge length passed to fill_from_dev_buffer(), while the source array was only 32 bytes, causing a stack out-of-bounds read in sg_copy_buffer(). The listed fix changes alloc_len to u32.
Likely exposure
Most production exposure is likely limited unless scsi_debug is enabled or loaded and users can issue SCSI generic requests to related devices. The source bundle lists Linux kernel versions as affected but does not provide distribution-specific package status.
Exploitation context
The evidence is from syzkaller and kernel KASAN output. The bundle does not cite active exploitation, and KEV is false. Treat this as a local kernel attack-surface issue until vendor advisories or asset evidence show broader exposure.
Researcher notes
The source evidence supports an out-of-bounds read in scsi_debug resp_readcap16(), not remote exploitation. The affected-version data is broad and commit-oriented, so confirm exact downstream exposure through kernel configuration, module state, and vendor backports.
Mitigation direction
- Update affected Linux kernels to versions containing the referenced stable fixes.
- Check Linux vendor advisories for distribution-specific fixed package versions.
- Disable or avoid loading scsi_debug where it is not operationally required.
- Restrict local access to SCSI generic devices where feasible.
Validation and detection
- Inventory Linux kernel versions across servers, appliances, and test hosts.
- Check whether the scsi_debug kernel module is built, available, or loaded.
- Review local access controls for SCSI generic device nodes.
- Confirm fixed kernel commits or vendor backports are present.
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
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CVE-2021-47191 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/3e20cb072679bdb47747ccc8bee3233a4cf0765aCVE reference, Linux
- https://git.kernel.org/stable/c/5b8bed6464ad6653586e30df046185fd816ad999CVE reference, Linux
- https://git.kernel.org/stable/c/4e3ace0051e7e504b55d239daab8789dd89b863cCVE 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.