LiveActive security incident?Get immediate response
CVE Record

CVE-2026-46243: smb: client: reject userspace cifs.spnego descriptions

In the Linux kernel, the following vulnerability has been resolved: smb: client: reject userspace cifs.spnego descriptions cifs.spnego key descriptions contain authority-bearing fields such as pid, uid, creduid, and upcall_target that cifs.upcall treats as kernel-originating inputs. However, userspace can also create keys of this type through request_key(2) or add_key(2), allowing those fields to be supplied without CIFS origin. Only accept cifs.spnego descriptions while CIFS is using its private spnego_cred to request the key.

HighCVSS 7.8Not KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-46243 is a local Linux kernel SMB/CIFS client flaw. A logged-in local user may be able to supply forged cifs.spnego key data that the CIFS upcall path treats as kernel-originated. The published impact is high for confidentiality, integrity, and availability.

Executive priority

Treat as a high-priority kernel update for Linux systems with local users or CIFS client usage. It is not shown as remotely exploitable or KEV-listed, but local privilege context and high impact justify prompt remediation.

Technical view

The issue is improper validation of userspace-created cifs.spnego key descriptions. Fields such as pid, uid, creduid, and upcall_target are authority-bearing, but request_key(2) or add_key(2) could create matching key types outside CIFS origin. The kernel fix accepts these descriptions only when CIFS uses its private spnego_cred.

Likely exposure

Exposure is most relevant on Linux systems running affected kernels where the SMB/CIFS client and cifs.upcall/SPNEGO authentication path are available. The CVSS vector is local, low complexity, low privilege, no user interaction.

Exploitation context

The bundle marks KEV as false, so active exploitation is not established here. A GitHub repository is tagged as exploit-related, indicating public exploit research or tooling may exist, but the bundle does not prove in-the-wild exploitation.

Researcher notes

Key questions are kernel branch, CIFS client use, keyring/SPNEGO configuration, and vendor backport status. The source data confirms the fix logic but does not provide complete distro-by-distro exposure beyond Red Hat references.

Mitigation direction

  • Apply vendor kernel updates that include the cifs.spnego validation fix.
  • For Red Hat systems, review the listed RHSA advisories for applicable packages.
  • If patching is delayed, reduce local account access on affected Linux hosts.
  • Review whether CIFS/SMB client functionality is required on exposed multi-user systems.
  • Track upstream Linux stable commits referenced for fixed kernel branches.

Validation and detection

  • Inventory Linux kernel versions against the affected and fixed versions in vendor advisories.
  • Confirm whether cifs.upcall and SMB/CIFS mounts are present on target systems.
  • Verify patched kernels include the referenced cifs.spnego rejection change.
  • Check Red Hat CVE and errata status for each deployed product stream.
  • Prioritize validation on multi-user servers and workstation fleets with local users.
Prepared
Confidence
medium
Sources
12

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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 · low confidence lookup

CWE-20: 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 lookup
cwe · low confidence lookup

CWE-825: 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 lookup
cve · low confidence lookup

CVE-2026-46243 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
High
CVSS
7.8 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Official CVE source material

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.

3CVSS vectors
5Timeline events
3ADP providers
43Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: pocAutomatable: noTechnical Impact: total

CVSS vector scores

3 official scores

We 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.

ScoreVersionSeverityVectorExploitImpactSource
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9CISA-ADP
7.8CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9redhat-SADP
7.1CVSS 3.1HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N1.85.2Linux

Vulnerability scoring details

Base CVSS 3.1 score

7.8High
CVSS 3.1 vector shape for CVE-2026-46243Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. ADP timelineredhat-SADP

    Reported to Red Hat.

  4. CVE publishedCVE Program

    The CVE record was published.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container
redhat-SADPkernel: Linux kernel: smb: client: reject userspace cifs.spnego descriptions
other:Red Hat severity ratingcvssV3_1
  • 2026-05-26T15:07:49.955Z: Reported to Red Hat.
  • 2026-05-26T00:00:00.000Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinuxf1d662a7d5e5322e583aad6b3cfec03d8f27b435, f1d662a7d5e5322e583aad6b3cfec03d8f27b435, f1d662a7d5e5322e583aad6b3cfec03d8f27b435, f1d662a7d5e5322e583aad6b3cfec03d8f27b435, f1d662a7d5e5322e583aad6b3cfec03d8f27b435, f1d662a7d5e5322e583aad6b3cfec03d8f27b435, f1d662a7d5e5322e583aad6b3cfec03d8f27b435, f1d662a7d5e5322e583aad6b3cfec03d8f27b435unaffected
LinuxLinux2.6.24, 0, 5.10.258, 5.15.209, 6.1.175, 6.6.142, 6.12.92, 6.18.34, 7.0.11, 7.1affected
Weakness

CWE details

CWE-20CWE-825

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-20 · source CWE mapping

Improper Input Validation

Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-825 · source CWE mapping

Expired Pointer Dereference

Expired Pointer Dereference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs