CVE-2024-56558 nfsd: make sure exp active before svc_export_show
A use-after-free vulnerability in the Linux kernel NFS server allows local attackers to trigger a system crash or warning by accessing export information.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2024-56558?
CVE-2024-56558 is a high-severity use after free vulnerability in Linux kernel, published on 27 Dec 2024. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
nfsd: make sure exp active before svc_export_show
The function `e_show` was called with protection from RCU. This only ensures that `exp` will not be freed. Therefore, the reference count for `exp` can drop to zero, which will trigger a refcount use-after-free warning when `exp_get` is called. To resolve this issue, use `cache_get_rcu` to ensure that `exp` remains active.
------------[ cut here ]------------ refcount_t: addition on 0; use-after-free. WARNING: CPU: 3 PID: 819 at lib/refcount.c:25 refcount_warn_saturate+0xb1/0x120 CPU: 3 UID: 0 PID: 819 Comm: cat Not tainted 6.12.0-rc3+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.1-2.fc37 04/01/2014 RIP: 0010:refcount_warn_saturate+0xb1/0x120 ... Call Trace: <TASK> e_show+0x20b/0x230 [nfsd] seq_read_iter+0x589/0x770 seq_read+0x1e5/0x270 vfs_read+0x125/0x530 ksys_read+0xc1/0x160 do_syscall_64+0x5f/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e
Weakness: CWE-416
Which versions are affected by CVE-2024-56558?
It affects 1 product.
Linux distribution packages (4)
kernel-livepatch-SLE15-SP3_Update_56 SUSE:Linux Enterprise Live Patching 15 SP3 | All versions | 2-150300.2.1 |
kernel-livepatch-SLE15-SP3_Update_57 SUSE:Linux Enterprise Live Patching 15 SP3 | All versions | 2-150300.2.1 |
kernel-livepatch-SLE15-SP4_Update_39 SUSE:Linux Enterprise Live Patching 15 SP4 | All versions | 2-150400.2.1 |
kernel-livepatch-SLE15-SP4_Update_40 SUSE:Linux Enterprise Live Patching 15 SP4 | All versions | 2-150400.2.1 |
Products include Linux kernel.
How do I fix CVE-2024-56558?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2024-56558 being exploited?
There is no known exploitation of CVE-2024-56558 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2024-56558, DEBIAN-CVE-2024-56558, GHSA-r5pj-8mrw-4gqj, SUSE-SU-2025:02456-1, SUSE-SU-2025:02467-1, SUSE-SU-2025:02469-1 and 2 more.