Security readout for executives and security teams
Plain-English summary
A memory-safety flaw exists in the Linux kernel’s SMB server while processing SMB2 file-open activity. The supplied CVSS assessment rates it critical because network access without credentials or user interaction may be sufficient, with potentially severe system impact. The cited evidence does not establish active exploitation.
Executive priority
Treat internet-facing or broadly reachable Linux SMB servers as urgent. Identify exposed systems immediately, restrict access, and apply vendor-confirmed kernel updates. Internal systems with tightly limited SMB reachability remain important but can follow exposure-based prioritization. Current evidence does not support claiming an ongoing exploitation campaign.
Technical view
In smb2_open(), opinfo is obtained from fp->f_opinfo using rcu_dereference(), but is dereferenced after rcu_read_unlock(). The object may therefore be reclaimed before use, creating a race-dependent use-after-free window. The supplied CVSS 3.1 vector is 9.8: network-accessible, low complexity, unauthenticated, and potentially high-impact.
Likely exposure
Potential exposure is concentrated on Linux hosts running the affected kernel SMB server with SMB reachable over a network. The bundle lists affected kernel entries spanning 5.15 through 7.0, but does not provide reliable distribution-package mappings. Vendor backports may change applicability.
Exploitation context
The bundle marks this CVE as absent from KEV, and no cited source demonstrates active exploitation, a public exploit, or confirmed code execution. The CVSS vector indicates a serious unauthenticated network attack surface, but practical reliability and outcomes are not established here.
Researcher notes
The affected-version data is ambiguous: it mixes release numbers with a repeated commit hash and supplies no distribution-package mapping. Six stable fix commits are referenced. Validate ancestry and vendor backports before declaring a host vulnerable or fixed. The sources establish a use-after-free condition but not a demonstrated exploitation primitive or outcome.
Mitigation direction
- Upgrade to a vendor-supported kernel containing the applicable stable fix or distribution backport.
- Check the Linux distribution vendor’s advisory for exact fixed package versions.
- Restrict SMB access to required trusted networks while remediation is pending.
- Disable the kernel SMB server where unnecessary, following service-impact review.
Validation and detection
- Inventory hosts running the kernel SMB server and record their active kernel builds.
- Confirm whether SMB is reachable from untrusted or unnecessary network segments.
- Verify the installed kernel contains a vendor backport or applicable referenced stable fix.
- Confirm the remediated kernel is active after installation and reboot.
- Review kernel logs for SMB crashes or memory errors; absence does not exclude exposure.
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-2026-43378 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
- Critical
- CVSS
- 9.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.
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:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H3.95.9LinuxVulnerability scoring details
Base CVSS 3.1 score
9.8CriticalVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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.
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/e1b21e6066615e7d3d3a7aa2677e415e563fd7ccCVE reference, Linux
- https://git.kernel.org/stable/c/b720c84087cb547f23ce03eab93568c1769e4556CVE reference, Linux
- https://git.kernel.org/stable/c/54b48ae83de8bb06e65079d96368efe359d4909cCVE reference, Linux
- https://git.kernel.org/stable/c/8f5b1a7cb009a93c48e9e334a2f59a660f9afc07CVE reference, Linux
- https://git.kernel.org/stable/c/190e5f808e8058640b408ccfed25440b441a718aCVE reference, Linux
- https://git.kernel.org/stable/c/1e689a56173827669a35da7cb2a3c78ed5c53680CVE 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.