high CVSS 7.8

CVE-2024-56764·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: ublk: detach gendisk from ublk device if add_disk() fails Inside ublk_abort_requests(), gendisk is grabbed for aborting all inflight requests. And ublk_abort_requests() is called when exiting the uring context or handling timeout. If add_disk() fails, the gendisk may have been freed when calling ublk_abort_requests(), so use-after-free can be caused when getting disk's reference in ublk_abort_requests(). Fixes the bug by detaching gendisk from ublk device if add_disk() fails.

Severity
high
Software
Kernel
Fixed in
6.12.8
Published
2025-01-06

Affected versions

From: 6.7

Until: 6.12.8

Fixed in: 6.12.8

How to fix this CVE

Update your Linux kernel to version 6.12.8 or later to resolve a use-after-free vulnerability in the ublk (userspace block device) subsystem. The vulnerability occurs when gendisk initialization fails, leaving freed memory references that can be accessed during request abort operations. Systems running kernel versions 6.7 through 6.12.7 should prioritize this update, particularly those using ublk for block device operations.

sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check kernel version with `uname -r` and compare against the affected range (6.7 to 6.12.7)
  2. Step 2: Verify ublk is enabled in kernel config: `cat /boot/config-$(uname -r) | grep CONFIG_BLK_DEV_UBLK`
  3. Step 3: Search kernel logs for use-after-free crashes: `sudo dmesg | grep -i 'use-after-free\|ublk\|gendisk'`
  4. Step 4: After patching, confirm new kernel version with `uname -r` shows 6.12.8 or later, then reboot if needed

FAQ

What is CVE-2024-56764?

CVE-2024-56764 is a use-after-free vulnerability in the Linux kernel's ublk (userspace block device) driver. When disk initialization fails, the gendisk structure is freed but still referenced during request abort operations, potentially causing memory corruption or kernel panic.

Is CVE-2024-56764 being actively exploited?

No, CVE-2024-56764 is not listed on the CISA Known Exploited Vulnerabilities catalog and no public exploits are currently available. However, it poses a significant denial-of-service risk for systems using ublk.

What versions of Kernel are affected by CVE-2024-56764?

Linux kernel versions 6.7 through 6.12.7 are affected. The vulnerability has been patched in kernel 6.12.8 and later.

How do I check if my server is vulnerable to CVE-2024-56764?

Run `uname -r` to check your kernel version. If it reports a version between 6.7 and 6.12.7, your system is vulnerable. Also verify ublk is enabled with `cat /boot/config-$(uname -r) | grep CONFIG_BLK_DEV_UBLK`.

Does Defensia detect CVE-2024-56764?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2024-56764 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2024-42256CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: cifs: Fix server re-repick on subrequest retry When a subrequest is marked for needing retry, netfs will call cifs_prepare_write() which will make cifs repick the server for the op before renegotiating credits; it then calls cifs_issue_write() which invokes smb2_async_writev() - which re-repicks the server. If a different server is then selected, this causes the increment of server->in_flight to happen against one record and the decrement to happen against another, leading to misaccounting. Fix this by just removing the repick code in smb2_async_writev(). As this is only called from netfslib-driven code, cifs_prepare_write() should always have been called first, and so server should never be NULL and the preparatory step is repeated in the event that we do a retry. The problem manifests as a warning looking something like: WARNING: CPU: 4 PID: 72896 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x3f0/0x9e0 [cifs] ... RIP: 0010:smb2_add_credits+0x3f0/0x9e0 [cifs] ... smb2_writev_callback+0x334/0x560 [cifs] cifs_demultiplex_thread+0x77a/0x11b0 [cifs] kthread+0x187/0x1d0 ret_from_fork+0x34/0x60 ret_from_fork_asm+0x1a/0x30 Which may be triggered by a number of different xfstests running against an Azure server in multichannel mode. generic/249 seems the most repeatable, but generic/215, generic/249 and generic/308 may also show it.
CVE-2024-36031CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: keys: Fix overwrite of key expiration on instantiation The expiry time of a key is unconditionally overwritten during instantiation, defaulting to turn it permanent. This causes a problem for DNS resolution as the expiration set by user-space is overwritten to TIME64_MAX, disabling further DNS updates. Fix this by restoring the condition that key_set_expiry is only called when the pre-parser sets a specific expiry.
CVE-2024-38612CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: sr: fix invalid unregister error path The error path of seg6_init() is wrong in case CONFIG_IPV6_SEG6_LWTUNNEL is not defined. In that case if seg6_hmac_init() fails, the genl_unregister_family() isn't called. This issue exist since commit 46738b1317e1 ("ipv6: sr: add option to control lwtunnel support"), and commit 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and null-ptr-deref") replaced unregister_pernet_subsys() with genl_unregister_family() in this error path.
CVE-2024-38623CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: Use variable length array instead of fixed size Should fix smatch warning: ntfs_set_label() error: __builtin_memcpy() 'uni->name' too small (20 vs 256)
CVE-2021-47548CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ethernet: hisilicon: hns: hns_dsaf_misc: fix a possible array overflow in hns_dsaf_ge_srst_by_port() The if statement: if (port >= DSAF_GE_NUM) return; limits the value of port less than DSAF_GE_NUM (i.e., 8). However, if the value of port is 6 or 7, an array overflow could occur: port_rst_off = dsaf_dev->mac_cb[port]->port_rst_off; because the length of dsaf_dev->mac_cb is DSAF_MAX_PORT_NUM (i.e., 6). To fix this possible array overflow, we first check port and if it is greater than or equal to DSAF_MAX_PORT_NUM, the function returns.

References

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2024-56764. Free for 1 server.

Get started free