NVD / CVE Program· CNA Linux

CVE-2026-64401: smb: client: resolve SWN tcon from live registrations

Noroxi assessment

Priority: Monitor (action score 31/100)

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: 0.12% (FIRST EPSS).
Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Linux Linux 0700f946659d0ab2352ec8a9b1c6fc74b13a27d7, 51d18db392e5386a7bb9e816d611f14e600cca3c, 91b8a58c6ac15c7db6518f696389933282f88da7.

Low priority for now. Upgrade to Linux Linux 0700f946659d0ab2352ec8a9b1c6fc74b13a27d7, 51d18db392e5386a7bb9e816d611f14e600cca3c, 91b8a58c6ac15c7db6518f696389933282f88da7 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: resolve SWN tcon from live registrations cifs_swn_notify() looks up a witness registration by id under cifs_swnreg_idr_mutex, drops the mutex, and then uses the registration's cached tcon pointer. That pointer is not a lifetime reference, and it is not a stable representative once cifs_get_swn_reg() lets multiple tcons for the same net/share name share one registration id. A same-share second mount can keep the cifs_swn_reg alive after the first tcon unregisters and is freed. The registration then still points at the freed first tcon, so taking tc_lock or incrementing tc_count through swnreg->tcon only moves the use-after-free earlier. Taking tc_lock while holding cifs_swnreg_idr_mutex also violates the documented CIFS lock order. Fix this by making the registration store only the stable witness identity: id, net name, share name, and notify flags. When a notify arrives, copy that identity under cifs_swnreg_idr_mutex, drop the mutex, then find and pin a live witness tcon that currently matches the net/share pair under the normal cifs_tcp_ses_lock -> tc_lock order. The notification path uses that pinned tcon directly and drops the reference when done. Registration and unregister messages now use the live tcon passed by the caller instead of a cached tcon in the registration. The final unregister send is folded into cifs_swn_unregister() while the registration is still protected by cifs_swnreg_idr_mutex. This removes the previous find/drop/reacquire raw-pointer window. The release path only removes the idr entry and frees the stable identity strings. This preserves the intended one-registration/many-tcon behavior: a registration id represents a net/share pair, and notify handling acts on a live representative selected at use time. It also preserves CLIENT_MOVE ordering for the representative tcon because the old-IP unregister is sent before cifs_swn_register() sends the new-IP register.

HighCVSS 7.8 · v3.1—No exploit Fix available

Memory safety

Published: Jul 25, 2026
Updated: Oct 19, 2026
EPSS: 0.1% · 2th percentile
CWE: CWE-416

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 31 / 40 · 7.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.1%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · Linux: 7.8; 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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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.

Vendor	Product	CPE
linux	linux kernel	cpe:2.3:o:linux:linux_kernel

Affected versions

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

linux linux kernel5.11 and later · before 6.1.178
linux linux kernel6.2 and later · before 6.6.145
linux linux kernel6.7 and later · before 6.12.97
linux linux kernel6.13 and later · before 6.18.39
linux linux kernel6.19 and later · before 7.1.4

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
- 5.11affected
- fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 and later · before 51d18db392e5386a7bb9e816d611f14e600cca3caffected · git
- fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 and later · before aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fdaffected · git
- fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 and later · before 945b4a4a54497db1dcb2f20ef801a84e884dac21affected · git
- fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 and later · before 91b8a58c6ac15c7db6518f696389933282f88da7affected · git
- fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 and later · before 0700f946659d0ab2352ec8a9b1c6fc74b13a27d7affected · git
- fed979a7e082bd9f25f9002c3c4f8740dacd0bc8 and later · before ec457f9afe5ae9538bdcd58fd4cb442b9787e183affected · git
- before 5.11not affected · semver
- 6.1.178 and later · up to and including 6.1.*not affected · semver
- 6.6.145 and later · up to and including 6.6.*not affected · semver

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
Debian:12	linux	before 6.1.180-1	6.1.180-1
Debian:12	linux-6.12	before 6.12.100-1~deb12u1	6.12.100-1~deb12u1
Debian:13	linux	before 6.12.100-1	6.12.100-1
Debian:14	linux	before 7.1.4-1	7.1.4-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

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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-2026-64392Jul 25, 2026 · ksmbd: use opener credentials for delete-on-close
36Monitor
← EarlierCVE-2026-64400Jul 25, 2026 · ksmbd: prevent path traversal bypass by restricting caseless retry
34Monitor
Later →CVE-2026-64403Jul 25, 2026 · Bluetooth: L2CAP: validate option length before reading conf opt value
28Monitor

Remediation

Which version to upgrade to

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

Product / package	Fixed version	Source
Linux Linux	0700f946659d0ab2352ec8a9b1c6fc74b13a27d7	Vendor (CNA)
Linux Linux	51d18db392e5386a7bb9e816d611f14e600cca3c	Vendor (CNA)
Linux Linux	91b8a58c6ac15c7db6518f696389933282f88da7	Vendor (CNA)
Linux Linux	945b4a4a54497db1dcb2f20ef801a84e884dac21	Vendor (CNA)
Linux Linux	aa3c0cab4b28c5007ec570c63e1d6ad6943ed0fd	Vendor (CNA)
Linux Linux	ec457f9afe5ae9538bdcd58fd4cb442b9787e183	Vendor (CNA)
debian:linux	6.1.180-1 · Debian:12	Package registry (OSV)
debian:linux-6.12	6.12.100-1~deb12u1 · Debian:12	Package 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.

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.

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

Someone with local access to the system can trigger it.
A low-privileged account is enough.
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: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

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

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

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

SSVC exploitation— → noneOct 16, 2026, 5:07 PM UTC
Fix✗ → ✓Sep 28, 2026, 10:11 PM UTC

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

References

git.kernel.org/stable/c/0700f946659d0ab2352ec8a9b1c6fc74b13a27d7

Show all references (5 more)

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

All records