# CVE-2024-56664: bpf, sockmap: Fix race between element replace and close()

> A race condition in the Linux kernel's BPF sockmap allows attackers to trigger use-after-free errors, potentially leading to privilege escalation or code execution.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 27 Dec 2024
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-54779, AZL-54812, BELL-CVE-2024-56664, DEBIAN-CVE-2024-56664, GHSA-22x4-j6vj-fmm5, UBUNTU-CVE-2024-56664

## What is CVE-2024-56664?

CVE-2024-56664 is a high-severity 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:

bpf, sockmap: Fix race between element replace and close()

Element replace (with a socket different from the one stored) may race
with socket's close() link popping & unlinking. __sock_map_delete()
unconditionally unrefs the (wrong) element:

// set map[0] = s0
map_update_elem(map, 0, s0)

// drop fd of s0
close(s0)
  sock_map_close()
    lock_sock(sk)               (s0!)
    sock_map_remove_links(sk)
      link = sk_psock_link_pop()
      sock_map_unlink(sk, link)
        sock_map_delete_from_link
                                        // replace map[0] with s1
                                        map_update_elem(map, 0, s1)
                                          sock_map_update_elem
                                (s1!)       lock_sock(sk)
                                            sock_map_update_common
                                              psock = sk_psock(sk)
                                              spin_lock(&stab->lock)
                                              osk = stab->sks[idx]
                                              sock_map_add_link(..., &stab->sks[idx])
                                              sock_map_unref(osk, &stab->sks[idx])
                                                psock = sk_psock(osk)
                                                sk_psock_put(sk, psock)
                                                  if (refcount_dec_and_test(&psock))
                                                    sk_psock_drop(sk, psock)
                                              spin_unlock(&stab->lock)
                                            unlock_sock(sk)
          __sock_map_delete
            spin_lock(&stab->lock)
            sk = *psk                        // s1 replaced s0; sk == s1
            if (!sk_test || sk_test == sk)   // sk_test (s0) != sk (s1); no branch
              sk = xchg(psk, NULL)
            if (sk)
              sock_map_unref(sk, psk)        // unref s1; sks[idx] will dangle
                psock = sk_psock(sk)
                sk_psock_put(sk, psock)
                  if (refcount_dec_and_test())
                    sk_psock_drop(sk, psock)
            spin_unlock(&stab->lock)
    release_sock(sk)

Then close(map) enqueues bpf_map_free_deferred, which finally calls
sock_map_free(). This results in some refcount_t warnings along with
a KASAN splat [1].

Fix __sock_map_delete(), do not allow sock_map_unref() on elements that
may have been replaced.

[1]:
BUG: KASAN: slab-use-after-free in sock_map_free+0x10e/0x330
Write of size 4 at addr ffff88811f5b9100 by task kworker/u64:12/1063

CPU: 14 UID: 0 PID: 1063 Comm: kworker/u64:12 Not tainted 6.12.0+ #125
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
Workqueue: events_unbound bpf_map_free_deferred
Call Trace:
 <TASK>
 dump_stack_lvl+0x68/0x90
 print_report+0x174/0x4f6
 kasan_report+0xb9/0x190
 kasan_check_range+0x10f/0x1e0
 sock_map_free+0x10e/0x330
 bpf_map_free_deferred+0x173/0x320
 process_one_work+0x846/0x1420
 worker_thread+0x5b3/0xf80
 kthread+0x29e/0x360
 ret_from_fork+0x2d/0x70
 ret_from_fork_asm+0x1a/0x30
 </TASK>

Allocated by task 1202:
 kasan_save_stack+0x1e/0x40
 kasan_save_track+0x10/0x30
 __kasan_slab_alloc+0x85/0x90
 kmem_cache_alloc_noprof+0x131/0x450
 sk_prot_alloc+0x5b/0x220
 sk_alloc+0x2c/0x870
 unix_create1+0x88/0x8a0
 unix_create+0xc5/0x180
 __sock_create+0x241/0x650
 __sys_socketpair+0x1ce/0x420
 __x64_sys_socketpair+0x92/0x100
 do_syscall_64+0x93/0x180
 entry_SYSCALL_64_after_hwframe+0x76/0x7e

Freed by task 46:
 kasan_save_stack+0x1e/0x40
 kasan_save_track+0x10/0x30
 kasan_save_free_info+0x37/0x60
 __kasan_slab_free+0x4b/0x70
 kmem_cache_free+0x1a1/0x590
 __sk_destruct+0x388/0x5a0
 sk_psock_destroy+0x73e/0xa50
 process_one_work+0x846/0x1420
 worker_thread+0x5b3/0xf80
 kthread+0x29e/0x360
 ret_from_fork+0x2d/0x70
 ret_from_fork_asm+0x1a/0x30

The bu
---truncated---

Weakness: CWE-416 (Use After Free), CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization)

## Which versions are affected by CVE-2024-56664?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-56664?

Apply the vendor's patch.

## Is CVE-2024-56664 being exploited?

There is no known exploitation of CVE-2024-56664 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-56664 and fix it if it is affected.

What it is: CVE-2024-56664 is a high-severity 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.
Exploitation: There is no known exploitation of CVE-2024-56664 in the wild and no public exploit code.

Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-56664/ (Markdown: https://insights.sbomify.com/CVE-2024-56664/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-56664
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-56664
- OSV: https://osv.dev/vulnerability/CVE-2024-56664

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-56664/
Summaries are generated and may contain mistakes; the official description above is the record.