NVD / CVE Program· CNA Linux

CVE-2026-64541: net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

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: 0.56% (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 1951bffbc6493ec34cff3956b29d4bc6606904a6, 3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb, 472e9d7c0d5b03be3ff91ff941f57da822b031bc.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1951bffbc6493ec34cff3956b29d4bc6606904a6, 3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb, 472e9d7c0d5b03be3ff91ff941f57da822b031bc 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: net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket smc_cdc_rx_handler() looks up the connection by token under the link group's conns_lock, drops the lock, and then dereferences conn and the smc_sock derived from it, ending in sock_hold(&smc->sk) inside smc_cdc_msg_recv(). No reference is held across the lock release. The only reference pinning the socket while the connection is discoverable in the link group is taken in smc_lgr_register_conn() (sock_hold) and dropped in __smc_lgr_unregister_conn() (sock_put), both under conns_lock. Once the handler drops conns_lock, a concurrent close() -> smc_release() -> smc_conn_free() -> smc_lgr_unregister_conn() can drop that reference and free the smc_sock, so the handler's later sock_hold() runs on freed memory: WARNING: lib/refcount.c:25 at refcount_warn_saturate Workqueue: rxe_wq do_work refcount_warn_saturate (lib/refcount.c:25) smc_cdc_msg_recv (net/smc/smc_cdc.c:430) smc_cdc_rx_handler (net/smc/smc_cdc.c:502) smc_wr_rx_tasklet_fn (net/smc/smc_wr.c:445) tasklet_action_common (kernel/softirq.c:938) handle_softirqs (kernel/softirq.c:622) Kernel panic - not syncing: panic_on_warn set Only SMC-R is affected. The SMC-D receive tasklet is stopped by tasklet_kill(&conn->rx_tsklet) in smc_conn_free() before the connection is unregistered, so it cannot run concurrently with the free. Take the socket reference while still holding conns_lock, so the registration reference can no longer be the last one, and drop it once the handler is done.

CriticalCVSS 9.8 · v3.1—No exploit Fix available

Published: Jul 27, 2026
Updated: Oct 19, 2026
EPSS: 0.5% · 46th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.5%

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.

—

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
- 4.18affected
- d7b0e37c1ac152905b18a5b9506179091a35b0b6 and later · before 8de4f665d0febfb92803dece377791a563fc7041affected · git
- d7b0e37c1ac152905b18a5b9506179091a35b0b6 and later · before 8145b432136285e01091815b48ceb2dae261f262affected · git
- d7b0e37c1ac152905b18a5b9506179091a35b0b6 and later · before 1951bffbc6493ec34cff3956b29d4bc6606904a6affected · git
- d7b0e37c1ac152905b18a5b9506179091a35b0b6 and later · before 647b19e5cc145a2f1f685ae8ff3805a17356888caffected · git
- d7b0e37c1ac152905b18a5b9506179091a35b0b6 and later · before 472e9d7c0d5b03be3ff91ff941f57da822b031bcaffected · git
- d7b0e37c1ac152905b18a5b9506179091a35b0b6 and later · before 3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bbaffected · git
- d7b0e37c1ac152905b18a5b9506179091a35b0b6 and later · before ce5aa8084329351086894aa34d77e40301d5bd3daffected · git
- d7b0e37c1ac152905b18a5b9506179091a35b0b6 and later · before 9d160b35cc34a2ba8229d07651468a7848325135affected · git
- before 4.18not 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 7.1.5-1	7.1.5-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
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CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
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CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
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Published before and after this one in the same product

← EarlierCVE-2026-64539Jul 27, 2026 · Bluetooth: eir: Fix stack OOB write when prepending the Flags AD
31Monitor
← EarlierCVE-2026-64540Jul 27, 2026 · usbnet: gl620a: fix out-of-bounds read in genelink_rx_fixup()
32Monitor
Later →CVE-2026-64543Jul 27, 2026 · tipc: fix use-after-free of the discoverer in tipc_disc_rcv()
31Monitor

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	1951bffbc6493ec34cff3956b29d4bc6606904a6	Vendor (CNA)
Linux Linux	3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb	Vendor (CNA)
Linux Linux	472e9d7c0d5b03be3ff91ff941f57da822b031bc	Vendor (CNA)
Linux Linux	647b19e5cc145a2f1f685ae8ff3805a17356888c	Vendor (CNA)
Linux Linux	8145b432136285e01091815b48ceb2dae261f262	Vendor (CNA)
Linux Linux	8de4f665d0febfb92803dece377791a563fc7041	Vendor (CNA)
Linux Linux	9d160b35cc34a2ba8229d07651468a7848325135	Vendor (CNA)
Linux Linux	ce5aa8084329351086894aa34d77e40301d5bd3d	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.

CVE-2026-645301 days apartnet/sched: cls_api: Handle TC_ACT_CONSUMED in tcf_qevent_handle
39Monitor
CVE-2026-645232 days apartnet/handshake: Take a long-lived file reference at submit
39Monitor
CVE-2026-639798 days apartnet/handshake: hand off the pinned file reference to accept_doit
39Monitor
CVE-2026-645648 days apartsctp: don't free the ASCONF's own transport in DEL-IP processing
39Monitor
CVE-2026-6812714 days apartila: reload IPv6 header after pskb_may_pull in checksum adjust
39Monitor
CVE-2026-6842614 days apartxfrm: fix stale skb->prev after async crypto steals a GSO segment
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.

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Bug bounty scope

No known public program.

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

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-26-0649 · Jul 28, 2026(Linux Kernel Güvenlik Bildirimi)

All national notices →

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-416 · Use After Free

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/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/1951bffbc6493ec34cff3956b29d4bc6606904a6

Show all references (7 more)

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

All records