CyberSecBulletin
CVE-2026-64541NVD status: Analyzed

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2026-64541 is a critical-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 8de4f665d0febfb92803dece377791a563fc7041, 8145b432136285e01091815b48ceb2dae261f262, 1951bffbc6493ec34cff3956b29d4bc6606904a6 as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.56% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Linux to 8de4f665d0febfb92803dece377791a563fc7041 or 8145b432136285e01091815b48ceb2dae261f262 or 1951bffbc6493ec34cff3956b29d4bc6606904a6 or 647b19e5cc145a2f1f685ae8ff3805a17356888c, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.10.261 or 5.15.212 or 6.1.178 or 6.6.145, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinuxd7b0e37c1ac152905b18a5b9506179091a35b0b6 up to, but not including, 8de4f665d0febfb92803dece377791a563fc7041; d7b0e37c1ac152905b18a5b9506179091a35b0b6 up to, but not including, 8145b432136285e01091815b48ceb2dae261f262; d7b0e37c1ac152905b18a5b9506179091a35b0b6 up to, but not including, 1951bffbc6493ec34cff3956b29d4bc6606904a6; d7b0e37c1ac152905b18a5b9506179091a35b0b6 up to, but not including, 647b19e5cc145a2f1f685ae8ff3805a17356888c; d7b0e37c1ac152905b18a5b9506179091a35b0b6 up to, but not including, 472e9d7c0d5b03be3ff91ff941f57da822b031bc; d7b0e37c1ac152905b18a5b9506179091a35b0b6 up to, but not including, 3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb; d7b0e37c1ac152905b18a5b9506179091a35b0b6 up to, but not including, ce5aa8084329351086894aa34d77e40301d5bd3d; d7b0e37c1ac152905b18a5b9506179091a35b0b6 up to, but not including, 9d160b35cc34a2ba8229d07651468a7848325135; and 1 more ranges8de4f665d0febfb92803dece377791a563fc7041, 8145b432136285e01091815b48ceb2dae261f262, 1951bffbc6493ec34cff3956b29d4bc6606904a6, 647b19e5cc145a2f1f685ae8ff3805a17356888c, 472e9d7c0d5b03be3ff91ff941f57da822b031bc, 3bfb96d9bc6a7ed0b99c7db329cc2e22a28d84bb
LinuxLinux Kernel4.18 up to, but not including, 5.10.261; 5.11 up to, but not including, 5.15.212; 5.16 up to, but not including, 6.1.178; 6.2 up to, but not including, 6.6.145; 6.7 up to, but not including, 6.12.97; 6.13 up to, but not including, 6.18.40; 6.19 up to, but not including, 7.1.5; 7.25.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.97, 6.18.40

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

Official description

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Use After Free

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.

How developers prevent this class of flaw

  • Choose a language that provides automatic memory management.
  • When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.

More Use After Free vulnerabilities (CWE-416)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Use After Free vulnerabilities

Spotted an error? Tell us.