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NVD / CVE Program· CNA Linux

CVE-2026-31709: smb: client: validate the whole DACL before rewriting it in cifsacl

Noroxi assessment

Priority: Monitor (action score 35/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.34% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 0a8cf165566ba55a39fd0f4de172119dd646d39a, 8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12, b78db9bddc84136f6a0bb49e8883cf200dfb87a8.

Low priority for now. Upgrade to Linux Linux 0a8cf165566ba55a39fd0f4de172119dd646d39a, 8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12, b78db9bddc84136f6a0bb49e8883cf200dfb87a8 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: smb: client: validate the whole DACL before rewriting it in cifsacl build_sec_desc() and id_mode_to_cifs_acl() derive a DACL pointer from a server-supplied dacloffset and then use the incoming ACL to rebuild the chmod/chown security descriptor. The original fix only checked that the struct smb_acl header fits before reading dacl_ptr->size or dacl_ptr->num_aces. That avoids the immediate header-field OOB read, but the rewrite helpers still walk ACEs based on pdacl->num_aces with no structural validation of the incoming DACL body. A malicious server can return a truncated DACL that still contains a header, claims one or more ACEs, and then drive replace_sids_and_copy_aces() or set_chmod_dacl() past the validated extent while they compare or copy attacker-controlled ACEs. Factor the DACL structural checks into validate_dacl(), extend them to validate each ACE against the DACL bounds, and use the shared validator before the chmod/chown rebuild paths. parse_dacl() reuses the same validator so the read-side parser and write-side rewrite paths agree on what constitutes a well-formed incoming DACL.

HighCVSS 8.8 · v3.1—No exploit Fix available
Published
May 1, 2026
Updated
Oct 19, 2026
EPSS
0.3% · 28th percentile

Report tools

JSON

Action score

35

Monitor

Low priority for now.

CVSS
35 / 40 · 8.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
8.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel5.12 and later · before 7.0.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.12affected
    • bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 and later · before b8603d9ae6c9087662b098619996bc4a8064319daffected · git
    • bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 and later · before c2abdebf72000a64603ced84d36ccbd164f11391affected · git
    • bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 and later · before 8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12affected · git
    • bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 and later · before d92f3f0b22414e7515696a02224d0af55e3004a3affected · git
    • bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 and later · before ff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5affected · git
    • bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 and later · before b78db9bddc84136f6a0bb49e8883cf200dfb87a8affected · git
    • bc3e9dd9d104ca1b75644eab87b38ce8a924aef4 and later · before 0a8cf165566ba55a39fd0f4de172119dd646d39aaffected · git
    • before 5.12not affected · semver
    • 5.15.210 and later · up to and including 5.15.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:10kernelbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64kbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-corebefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-debugbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-debug-corebefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-debug-modulesbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-corebefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-debug-modules-extrabefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-modulesbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-modules-corebefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-64k-modules-extrabefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-abi-stablelistsbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-corebefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-cross-headersbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-debugbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-debug-corebefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-debug-modulesbefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2
AlmaLinux:10kernel-debug-modules-corebefore 6.12.0-211.20.1.el10_26.12.0-211.20.1.el10_2

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2026-31707May 1, 2026 · ksmbd: validate response sizes in ipc_validate_msg()
    28Monitor
  • ← EarlierCVE-2026-31708May 1, 2026 · smb: client: fix OOB read in smb2_ioctl_query_info QUERY_INFO path
    32Monitor
  • Later →CVE-2026-31711May 1, 2026 · smb: server: fix active_num_conn leak on transport allocation failure
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux0a8cf165566ba55a39fd0f4de172119dd646d39aVendor (CNA)
Linux Linux8e47d297e7cf9a6029a0d38e7b22faba7d7aaf12Vendor (CNA)
Linux Linuxb78db9bddc84136f6a0bb49e8883cf200dfb87a8Vendor (CNA)
Linux Linuxb8603d9ae6c9087662b098619996bc4a8064319dVendor (CNA)
Linux Linuxc2abdebf72000a64603ced84d36ccbd164f11391Vendor (CNA)
Linux Linuxd92f3f0b22414e7515696a02224d0af55e3004a3Vendor (CNA)
Linux Linuxff0ca46b13b9ef6edbcd238a3b6caacfef8ba0e5Vendor (CNA)
almalinux:kernel5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-devel-matched5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-devel-matched5.14.0-687.12.1.el9_8 · AlmaLinux:9Package registry (OSV)
debian:linux6.1.176-1 · Debian:12Package registry (OSV)
opensuse:kernel-source7.0.7-1.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:kernel-64k-debug-debuginfo0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel-matched0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debuginfo0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel-matched0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-debuginfo0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel-matched0:5.14.0-687.12.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

+5

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. SSVC exploitation— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (19 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records