CyberSecBulletin
CVE-2025-38443NVD status: Analyzed

Linux: Use After Free

Published Updated By the CyberSecBulletin desk

CVE-2025-38443 is a high-severity use after free vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions cb121c47f364b51776c4db904a6a5a90ab0a7ec5, 91fa560c73a8126868848ed6cd70607cbf8d87e2, d46186eb7bbd9a11c145120f2d77effa8d4d44c2 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 0.18% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update Linux to cb121c47f364b51776c4db904a6a5a90ab0a7ec5 or 91fa560c73a8126868848ed6cd70607cbf8d87e2 or d46186eb7bbd9a11c145120f2d77effa8d4d44c2 or 8586552df591e0a367eff44af0c586213eeecc3f, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.189 or 6.1.146 or 6.6.99 or 6.12.39, whichever matches your release line, or a later version.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux6497ef8df568afbf5f3e38825a4590ff41611a54 up to, but not including, cb121c47f364b51776c4db904a6a5a90ab0a7ec5; 6497ef8df568afbf5f3e38825a4590ff41611a54 up to, but not including, 91fa560c73a8126868848ed6cd70607cbf8d87e2; 6497ef8df568afbf5f3e38825a4590ff41611a54 up to, but not including, d46186eb7bbd9a11c145120f2d77effa8d4d44c2; 6497ef8df568afbf5f3e38825a4590ff41611a54 up to, but not including, 8586552df591e0a367eff44af0c586213eeecc3f; 6497ef8df568afbf5f3e38825a4590ff41611a54 up to, but not including, 002aca89753f666d878ca0eb8584c372684ac4ba; 6497ef8df568afbf5f3e38825a4590ff41611a54 up to, but not including, aa9552438ebf015fc5f9f890dbfe39f0c53cf37e; 5.14cb121c47f364b51776c4db904a6a5a90ab0a7ec5, 91fa560c73a8126868848ed6cd70607cbf8d87e2, d46186eb7bbd9a11c145120f2d77effa8d4d44c2, 8586552df591e0a367eff44af0c586213eeecc3f, 002aca89753f666d878ca0eb8584c372684ac4ba, aa9552438ebf015fc5f9f890dbfe39f0c53cf37e
LinuxLinux Kernel5.14 up to, but not including, 5.15.189; 5.16 up to, but not including, 6.1.146; 6.2 up to, but not including, 6.6.99; 6.7 up to, but not including, 6.12.39; 6.13 up to, but not including, 6.15.7; 6.165.15.189, 6.1.146, 6.6.99, 6.12.39, 6.15.7
DebianDebian Linux11.0Not stated

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
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: nbd: fix uaf in nbd_genl_connect() error path There is a use-after-free issue in nbd: block nbd6: Receive control failed (result -104) block nbd6: shutting down sockets ================================================================== BUG: KASAN: slab-use-after-free in recv_work+0x694/0xa80 drivers/block/nbd.c:1022 Write of size 4 at addr ffff8880295de478 by task kworker/u33:0/67 CPU: 2 UID: 0 PID: 67 Comm: kworker/u33:0 Not tainted 6.15.0-rc5-syzkaller-00123-g2c89c1b655c0 #0 PREEMPT(full) Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 Workqueue: nbd6-recv recv_work Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xc3/0x670 mm/kasan/report.c:521 kasan_report+0xe0/0x110 mm/kasan/report.c:634 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0xef/0x1a0 mm/kasan/generic.c:189 instrument_atomic_read_write include/linux/instrumented.h:96 [inline] atomic_dec include/linux/atomic/atomic-instrumented.h:592 [inline] recv_work+0x694/0xa80 drivers/block/nbd.c:1022 process_one_work+0x9cc/0x1b70 kernel/workqueue.c:3238 process_scheduled_works kernel/workqueue.c:3319 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3400 kthread+0x3c2/0x780 kernel/kthread.c:464 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK> nbd_genl_connect() does not properly stop the device on certain error paths after nbd_start_device() has been called. This causes the error path to put nbd->config while recv_work continue to use the config after putting it, leading to use-after-free in recv_work. This patch moves nbd_start_device() after the backend file creation.

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: no, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Recent Use After Free vulnerabilities

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