Security readout for executives and security teams
Plain-English summary
A Linux SMB client indexing error can mishandle compound command responses and potentially access memory outside a response-buffer array. Systems using an affected kernel to communicate with SMB services may face confidentiality, integrity, or availability impact. The supplied CVSS rating is 9.8, but the sources do not establish real-world exploitation.
Executive priority
Treat this as an urgent kernel patching and exposure-validation issue for SMB-using Linux systems. Prioritize externally connected, user-facing, and high-value hosts, while requiring package-level confirmation from each Linux distributor. Escalation should reflect the critical CVSS score, tempered by the absence of supplied evidence for active exploitation.
Technical view
The flaw is in smb2_compound_op(). Its response-processing loop uses incorrect indices when accessing response buffers. If a computed index reaches or exceeds MAX_COMPOUND, an out-of-bounds access may occur. The kernel references provide corrective commits, but the bundle does not describe the precise memory-safety outcome, reproducibility conditions, or demonstrated code execution.
Likely exposure
Prioritize Linux systems whose kernels match the bundle’s affected identifiers and that use the SMB client to process network responses. Actual distribution package exposure requires vendor-specific mapping because the supplied version data mixes release numbers and commit identifiers. Systems not using the SMB client have lower practical exposure, although installed vulnerable code should still be updated.
Exploitation context
The CVSS vector describes network-reachable, low-complexity exploitation requiring neither privileges nor user interaction. However, CISA KEV status is false, and the supplied sources provide no evidence of active exploitation, public proof-of-concept availability, or confirmed attacks. Treat the score as potential severity, not proof of current exploitation.
Researcher notes
The source bundle identifies wrong response-buffer indexing and a possible index at or above MAX_COMPOUND. It does not specify the resulting primitive, attacker-controlled fields, crash evidence, affected configuration prerequisites, or exploitability beyond CVSS. The affected-version representation is ambiguous, including release numbers, commit hashes, and an entry of "0"; validate against upstream commits and distributor mappings.
Mitigation direction
- Apply a vendor-supported kernel update incorporating the relevant linked stable-kernel fix.
- Reboot into the updated kernel where required, then confirm the running version.
- Check distribution security guidance for package-specific affected and fixed versions.
- Until patched, limit SMB client connections to trusted, necessary services.
- Reduce unnecessary SMB network reachability using existing segmentation and access controls.
Validation and detection
- Record each system’s running kernel version and distribution package release.
- Compare versions with the CVE record and applicable distribution security advisory.
- Confirm the installed kernel contains the relevant stable-kernel correction.
- Identify hosts actively using the Linux SMB client or configured SMB mounts.
- After updating, verify systems booted the corrected kernel rather than an older installed kernel.
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-2025-39975 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/ba7bcfd52c66dd1c2dfa5142aca7e4a70b62dfa5CVE reference, Linux
- https://git.kernel.org/stable/c/bfb1e2aad1fecef8320fd71332acde0d53a8d699CVE reference, Linux
- https://git.kernel.org/stable/c/093615fc76063ea08d454ba86677ce64c736e806CVE reference, Linux
- https://git.kernel.org/stable/c/fbe2dc6a9c7318f7263f5e4d50f6272b931c5756CVE 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.