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NVD / CVE Program· CNA Linux

CVE-2026-31609: smb: client: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush()

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 22b7c1c619d808aec4cad3dc42103345e370d107, 27b7c3e916218b5eb2ee350211140e961bfc49be, 6.18.24; azl3 kernel 6.6.130.1-3 on Azure Linux 3.0 6.6.134.1-2; azl3 kernel 6.6.134.1-2 on Azure Linux 3.0 6.6.134.1-2.

Low priority for now. Upgrade to Linux Linux 22b7c1c619d808aec4cad3dc42103345e370d107, 27b7c3e916218b5eb2ee350211140e961bfc49be, 6.18.24; azl3 kernel 6.6.130.1-3 on Azure Linux 3.0 6.6.134.1-2; azl3 kernel 6.6.134.1-2 on Azure Linux 3.0 6.6.134.1-2 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: avoid double-free in smbd_free_send_io() after smbd_send_batch_flush() smbd_send_batch_flush() already calls smbd_free_send_io(), so we should not call it again after smbd_post_send() moved it to the batch list.

CriticalCVSS 9.8 · v3.1—No exploit Fix available
Published
Apr 24, 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

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-31609

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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 kernelbefore 6.18.24
  • linux linux kernel6.19 and later · before 6.19.14
  • linux linux kernel7.0 and later · before 7.0.1

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

    • 7.0affected
    • cca0526ef2344cab6944d7f441fc24e152da031b and later · before a9940dcbe5cb92482c04efc7341039ddf7dbf607affected · git
    • 37b5c06956183b65e6808b509cf637632016cdf7 and later · before 22b7c1c619d808aec4cad3dc42103345e370d107affected · git
    • 21538121efe6c8c5b51c742fa02cbe820bc48714 and later · before f9a162c2bbcd0ac85bd07c5b37cf20286048b65caffected · git
    • 21538121efe6c8c5b51c742fa02cbe820bc48714 and later · before 27b7c3e916218b5eb2ee350211140e961bfc49beaffected · git
    • 6.18.11 and later · before 6.18.24affected · semver
    • 6.19.1 and later · before 6.19.14affected · semver
    • before 7.0not affected · semver
    • 6.18.24 and later · up to and including 6.18.*not affected · semver
    • 6.19.14 and later · up to and including 6.19.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:14linuxbefore 6.19.14-16.19.14-1

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-2026-31606Apr 24, 2026 · usb: gadget: f_hid: don't call cdev_init while cdev in use
    22Monitor
  • ← EarlierCVE-2026-31607Apr 24, 2026 · usbip: validate number_of_packets in usbip_pack_ret_submit()
    39Monitor
  • Later →CVE-2026-31611Apr 24, 2026 · ksmbd: require 3 sub-authorities before reading sub_auth[2]
    34Monitor

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 Linux22b7c1c619d808aec4cad3dc42103345e370d107Vendor (CNA)
Linux Linux27b7c3e916218b5eb2ee350211140e961bfc49beVendor (CNA)
Linux Linux6.18.24Vendor (CNA)
Linux Linux6.19.14Vendor (CNA)
Linux Linuxa9940dcbe5cb92482c04efc7341039ddf7dbf607Vendor (CNA)
Linux Linuxf9a162c2bbcd0ac85bd07c5b37cf20286048b65cVendor (CNA)
azl3 kernel 6.6.130.1-3 on Azure Linux 3.06.6.134.1-2 · CBL-Mariner ReleasesMicrosoft (MSRC)
azl3 kernel 6.6.134.1-2 on Azure Linux 3.06.6.134.1-2 · CBL-Mariner ReleasesMicrosoft (MSRC)
cbl2 kernel 5.15.202.1-1 on CBL-Mariner 2.0Release NotesMicrosoft (MSRC)
debian:linux6.19.14-1 · Debian:14Package registry (OSV)

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.

  • CVE-2026-316080 days apartsmb: server: avoid double-free in smb_direct_free_sendmsg after smb_direct_flush_send_list()
    39Monitor
  • CVE-2026-430117 days apartnet/x25: Fix potential double free of skb
    39Monitor
  • CVE-2026-4341414 days apartscsi: qla2xxx: Completely fix fcport double free
    39Monitor
  • CVE-2026-5299361 days aparttipc: fix double-free in tipc_buf_append()
    39Monitor
  • CVE-2026-6388886 days apartscsi: target: iscsi: Fix CRC overread and double-free in iscsit_handle_text_cmd()
    39Monitor
  • CVE-2026-6438692 days apartsmb: client: fix query_info() replay double-free
    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 (3 more)

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

All records