CVE-2024-56672: blk-cgroup: Fix UAF in blkcg_unpin_online()
Vulnerability summary
CVE-2024-56672 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.27% chance of exploitation in the next 30 days, higher than 19.6% of scored vulnerabilities.
Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 37 · Related 32Timeline
- 27-12-2024PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.0HighCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:HDiffers
- NVDNIST7.0HighCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:HDiffers
EPSS trend
Probability
0.27%
Chance of exploitation in the next 30 days
Percentile
20%
Versus all other CVEs
30-day change
No change 0.00 pp
From 0.27% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu122 products
- linux< 5.15.0-134.145 | < 6.8.0-57.59
- linux-allwinner-5.19All versions (No fix recorded)
- linux-aws< 5.15.0-1079.86 | < 6.8.0-1026.28
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 4308a434e5e08c78676aa66bc626ef78cbef0883, < 83f5a87ee8caa76a917f59912a74d6811f773c67 | ≥ 4308a434e5e08c78676aa66bc626ef78cbef0883, < 8a07350fe070017a887433f4d6909433955be5f1 | ≥ 4308a434e5e08c78676aa66bc626ef78cbef0883, < 64afc6fe24c9896c0153e5a199bcea241ecb0d5c | ≥ 4308a434e5e08c78676aa66bc626ef78cbef0883, < 5baa28569c924d9a90d036c2aaab79f791fedaf8 | ≥ 4308a434e5e08c78676aa66bc626ef78cbef0883, < 29d1e06560f0f6179062ac638b4064deb637d1ad | ≥ 4308a434e5e08c78676aa66bc626ef78cbef0883, < 86e6ca55b83c575ab0f2e105cf08f98e58d3d7af | 5.7
- linux_kernel≥ 5.7, < 6.1.121 | ≥ 6.2, < 6.6.67 | ≥ 6.7, < 6.12.6 | 6.13:rc1 | 6.13:rc2
Debian1 product
- linux< 6.1.123-1 | < 6.12.6-1
3 vendors · 125 products
