CVE-2024-56672: Linux kernel · blk-cgroup: Fix UAF in blkcg_unpin_online()
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 7.8 High · fixed in 5.15.0-1080.87~20.04.1 : patch Linux kernel soon.
Data as of 29 Oct 2026, 22:35 UTC
- Patch
- Available – fixed in 5.15.0-1080.87~20.04.1, 5.15.0-1082.91~20.04.1, 5.15.0-1078.87~20.04.1 +59
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 27 Dec 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
- ubuntu.com/security/notices/USN-7322-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7323-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7327-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7328-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7329-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7331-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7323-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7328-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7328-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7380-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7381-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7388-1 (opens in a new tab)
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 24.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-6.11pkg:deb/ubuntu/linux-azure-6.11?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-azure-nvidiapkg:deb/ubuntu/linux-azure-nvidia?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
In the Linux kernel, the following vulnerability has been resolved: blk-cgroup: Fix UAF in blkcg_unpin_online() blkcg_unpin_online() walks up the blkcg hierarchy putting the online pin. To walk up, it uses blkcg_parent(blkcg) but it was calling that after blkcg_destroy_blkgs(blkcg) which could free the blkcg, leading to the following UAF: ================================================================== BUG: KASAN: slab-use-after-free in blkcg_unpin_online+0x15a/0x270 Read of size 8 at addr ffff8881057678c0 by task kworker/9:1/117 CPU: 9 UID: 0 PID: 117 Comm: kworker/9:1 Not tainted 6.13.0-rc1-work-00182-gb8f52214c61a-dirty #48 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS unknown 02/02/2022 Workqueue: cgwb_release cgwb_release_workfn Call Trace: <TASK> dump_stack_lvl+0x27/0x80 print_report+0x151/0x710 kasan_report+0xc0/0x100 blkcg_unpin_online+0x15a/0x270 cgwb_release_workfn+0x194/0x480 process_scheduled_works+0x71b/0xe20 worker_thread+0x82a/0xbd0 kthread+0x242/0x2c0 ret_from_fork+0x33/0x70 ret_from_fork_asm+0x1a/0x30 </TASK> ... Freed by task 1944: kasan_save_track+0x2b/0x70 kasan_save_free_info+0x3c/0x50 __kasan_slab_free+0x33/0x50 kfree+0x10c/0x330 css_free_rwork_fn+0xe6/0xb30 process_scheduled_works+0x71b/0xe20 worker_thread+0x82a/0xbd0 kthread+0x242/0x2c0 ret_from_fork+0x33/0x70 ret_from_fork_asm+0x1a/0x30 Note that the UAF is not easy to trigger as the free path is indirected behind a couple RCU grace periods and a work item execution. I could only trigger it with artifical msleep() injected in blkcg_unpin_online(). Fix it by reading the parent pointer before destroying the blkcg's blkg's.
References
- ubuntu.com/security/CVE-2024-56672 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2024-56672 (opens in a new tab)
- git.kernel.org/linus/86e6ca55b83c575ab0f2e105cf08f98e58d3d7af (opens in a new tab)
- git.kernel.org/stable/c/29d1e06560f0f6179062ac638b4064deb637d1ad (opens in a new tab)
- git.kernel.org/stable/c/5baa28569c924d9a90d036c2aaab79f791fedaf8 (opens in a new tab)
- git.kernel.org/stable/c/64afc6fe24c9896c0153e5a199bcea241ecb0d5c (opens in a new tab)
- git.kernel.org/stable/c/86e6ca55b83c575ab0f2e105cf08f98e58d3d7af (opens in a new tab)
- ubuntu.com/security/notices/USN-7322-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7323-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7327-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7328-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7329-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7331-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7323-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7328-2 (opens in a new tab)
- ubuntu.com/security/notices/USN-7328-3 (opens in a new tab)
- ubuntu.com/security/notices/USN-7380-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7381-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7388-1 (opens in a new tab)
- ubuntu.com/security/notices/USN-7389-1 (opens in a new tab)