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Vulnerabilities

Vulnerability · CVE-2026-64541

net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

Published Jul 27, 2026 · catalog updated Nov 4, 2026 · Linux Linux

Last checked Nov 7, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-64541. EPSS is 0.56%. Act only if a listed version of Linux Linux is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
Critical9.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.56%
Remediation
Vendor / distro source
Affected products
Linux Kernel · vendor Linux Linux

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Linux Kernel4.18.0 → 5.10.261; 5.11.0 → 5.15.212; 5.16.0 → 6.1.178
  • vendor Linux Linuxversion unspecified

How to fix CVE-2026-64541

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-64541. EPSS is 0.56%. Act only if a listed version of Linux Linux is installed.

Which versions are affected?

Compare what you have installed with Kernel 4.18.0 → 5.10.261; 5.11.0 → 5.15.212; 5.16.0 → 6.1.178. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.56%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Ubuntu security

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 19, 2026 · CVE.org

    Updated

    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.

  2. Nov 4, 2026 · BSI CERT-Bund

    Detected

    CVE-2026-64541 is listed by Linux Kernel: Mehrere Schwachstellen.

  3. Nov 4, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    Kernel fixed in 5.10.261; Kernel fixed in 5.15.212; Kernel fixed in 6.1.178; Kernel fixed in 6.6.145

  4. Nov 4, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    Kernel fixed in 5.10.261; 5.11.0

  5. Nov 4, 2026 · OpenSSF OSV / OSV Scanner

    Updated

    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.

Sources

  • BSI CERT-BundGovernment advisoryCVE-2026-64541

    Linux Kernel: Mehrere Schwachstellen

    wid.cert-bund.de
  • CVE.orgVulnerability recordCVE-2026-64541

    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

    cve.org
  • OpenSSF OSV / OSV ScannerPackage advisoryCVE-2026-64541

    net/smc: fix UAF in smc_cdc_rx_handler() by pinning the socket

    osv.dev
  • Ubuntu Security NoticesVendor advisoryCVE-2026-64541

    It was discovered that some AMD processors did not properly perform Reverse Map Table (RMP) checks when the IOMMU accessed certain host buffers. A local attacker with hypervisor access could possibly use this to trigger an out-of-bounds condition and compromise the integrity of S

    ubuntu.com

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • Ubuntu Security NoticesNov 7, 2026
  • OpenSSF OSV / OSV ScannerNov 5, 2026
  • CVE.orgNov 4, 2026
  • BSI CERT-BundNov 4, 2026