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NVD / CVE Program· CNA Linux

CVE-2026-64383: smb: client: fix double-free in SMB2_flush() replay

Noroxi assessment

Priority: Monitor (action score 39/100)

  • 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: 0.45% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: Linux Linux 013a9a3da46c5dabcf18f65ea6a47874ba12a15d, 3407240cde132a4b72d6429a2625a09a2f78adaf, 4be31c943a3a27a5a0251dbb8f5cb89059ec3d5a; azl3 kernel 6.6.144.1-1 on Azure Linux 3.0 6.6.145.2-1.

Low priority for now. Upgrade to Linux Linux 013a9a3da46c5dabcf18f65ea6a47874ba12a15d, 3407240cde132a4b72d6429a2625a09a2f78adaf, 4be31c943a3a27a5a0251dbb8f5cb89059ec3d5a; azl3 kernel 6.6.144.1-1 on Azure Linux 3.0 6.6.145.2-1 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: fix double-free in SMB2_flush() replay SMB2_flush() keeps its response buffer bookkeeping across replay attempts. If a replayable flush response is received and the retry then fails before cifs_send_recv() stores a replacement response, flush_exit will free the stale response pointer a second time. Reinitialize resp_buftype and rsp_iov at the top of the replay loop so cleanup only acts on response state produced by the current attempt. This fixes a double-free without changing replay handling for successful requests.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Jul 25, 2026
Updated
Oct 19, 2026
EPSS
0.4% · 39th percentile

Report tools

JSON

Action score

39

Monitor

Low priority for now.

CVSS
39 / 40 · 9.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · Linux
9.8
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.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • 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 kernel6.6.32 and later · before 6.6.145
  • linux linux kernel6.8.1 and later · before 6.12.96
  • linux linux kernel6.13 and later · before 6.18.39
  • linux linux kernel6.19 and later · before 7.1.4
  • linux linux kernel6.8

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

    • 6.8affected
    • 433042a91f9373241307725b52de573933ffedbf and later · before 6e27f40b682a5e42a2daae3ce6d96f0e0e16dedbaffected · git
    • 4f1fffa2376922f3d1d506e49c0fd445b023a28e and later · before 878757163eea684750107a31ea134c103863515daffected · git
    • 4f1fffa2376922f3d1d506e49c0fd445b023a28e and later · before 3407240cde132a4b72d6429a2625a09a2f78adafaffected · git
    • 4f1fffa2376922f3d1d506e49c0fd445b023a28e and later · before 013a9a3da46c5dabcf18f65ea6a47874ba12a15daffected · git
    • 4f1fffa2376922f3d1d506e49c0fd445b023a28e and later · before 4be31c943a3a27a5a0251dbb8f5cb89059ec3d5aaffected · git
    • 6.6.32 and later · before 6.6.145affected · semver
    • before 6.8not affected · semver
    • 6.6.145 and later · up to and including 6.6.*not affected · semver
    • 6.12.96 and later · up to and including 6.12.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:10kernel-64k-debug-develbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-64k-debug-devel-matchedbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-64k-develbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-64k-devel-matchedbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-debug-develbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-debug-devel-matchedbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-develbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-devel-matchedbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-docbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-headersbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-zfcpdump-develbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10kernel-zfcpdump-devel-matchedbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10perfbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:10python3-perfbefore 6.12.0-211.59.1.el10_26.12.0-211.59.1.el10_2
AlmaLinux:9kernelbefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64kbefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64k-corebefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64k-debugbefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64k-debug-corebefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64k-debug-modulesbefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64k-debug-modules-corebefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64k-debug-modules-extrabefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64k-modulesbefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8
AlmaLinux:9kernel-64k-modules-corebefore 5.14.0-687.51.1.el9_85.14.0-687.51.1.el9_8

+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-2026-64381Jul 25, 2026 · smb: client: Fix next buffer leak in receive_encrypted_standard()
    31Monitor
  • ← EarlierCVE-2026-64382Jul 25, 2026 · smb: client: fix double-free in SMB2_open() replay
    35Monitor
  • Later →CVE-2026-64384Jul 25, 2026 · smb: client: fix change notify replay double-free
    39Monitor

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 Linux013a9a3da46c5dabcf18f65ea6a47874ba12a15dVendor (CNA)
Linux Linux3407240cde132a4b72d6429a2625a09a2f78adafVendor (CNA)
Linux Linux4be31c943a3a27a5a0251dbb8f5cb89059ec3d5aVendor (CNA)
Linux Linux6.6.145Vendor (CNA)
Linux Linux6e27f40b682a5e42a2daae3ce6d96f0e0e16dedbVendor (CNA)
Linux Linux878757163eea684750107a31ea134c103863515dVendor (CNA)
azl3 kernel 6.6.144.1-1 on Azure Linux 3.06.6.145.2-1 · CBL-Mariner ReleasesMicrosoft (MSRC)
almalinux:kernel5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-core5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-core5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-core5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-debug-modules-extra5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-modules5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-modules-core5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-64k-modules-extra5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
almalinux:kernel-abi-stablelists5.14.0-687.51.1.el9_8 · AlmaLinux:9Package registry (OSV)
debian:linux6.12.96-1 · Debian:13Package registry (OSV)
debian:linux-6.126.12.100-1~deb12u1 · Debian:12Package registry (OSV)
red hat:kernel-64k-debug-debuginfo0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel-matched0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debuginfo0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel-matched0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-debuginfo0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel-matched0:5.14.0-687.51.1.el9_8 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

+4

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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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.

  • CVE-2026-643840 days apartsmb: client: fix change notify replay double-free
    39Monitor
  • CVE-2026-643850 days apartsmb: client: fix double-free in SMB2_ioctl() replay
    39Monitor
  • CVE-2026-643860 days apartsmb: client: fix query_info() replay double-free
    39Monitor
  • CVE-2026-643870 days apartsmb: client: fix query directory replay double-free
    39Monitor
  • CVE-2026-638886 days apartscsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
    39Monitor
  • CVE-2026-5299331 days aparttipc: fix double-free in tipc_buf_append()
    39Monitor

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.
  • No user action is required.
  • 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
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-415 · Double Free

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

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

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

References

Show all references (4 more)

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

All records