# CVE-2022-49840: bpf, test_run: Fix alignment problem in bpf_prog_test_run_skb()

> A use-after-free vulnerability in the Linux kernel BPF test_run component allows attackers to cause a denial of service or potentially execute code via unaligned memory access.

- **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:** 1 May 2025
- **Updated:** 11 May 2026
- **Also known as:** DEBIAN-CVE-2022-49840, GHSA-7crj-grwh-6247, UBUNTU-CVE-2022-49840

## What is CVE-2022-49840?

CVE-2022-49840 is a high-severity use after free vulnerability in Linux kernel, published on 1 May 2025. 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, test_run: Fix alignment problem in bpf_prog_test_run_skb()

We got a syzkaller problem because of aarch64 alignment fault
if KFENCE enabled. When the size from user bpf program is an odd
number, like 399, 407, etc, it will cause the struct skb_shared_info's
unaligned access. As seen below:

  BUG: KFENCE: use-after-free read in __skb_clone+0x23c/0x2a0 net/core/skbuff.c:1032

  Use-after-free read at 0xffff6254fffac077 (in kfence-#213):
   __lse_atomic_add arch/arm64/include/asm/atomic_lse.h:26 [inline]
   arch_atomic_add arch/arm64/include/asm/atomic.h:28 [inline]
   arch_atomic_inc include/linux/atomic-arch-fallback.h:270 [inline]
   atomic_inc include/asm-generic/atomic-instrumented.h:241 [inline]
   __skb_clone+0x23c/0x2a0 net/core/skbuff.c:1032
   skb_clone+0xf4/0x214 net/core/skbuff.c:1481
   ____bpf_clone_redirect net/core/filter.c:2433 [inline]
   bpf_clone_redirect+0x78/0x1c0 net/core/filter.c:2420
   bpf_prog_d3839dd9068ceb51+0x80/0x330
   bpf_dispatcher_nop_func include/linux/bpf.h:728 [inline]
   bpf_test_run+0x3c0/0x6c0 net/bpf/test_run.c:53
   bpf_prog_test_run_skb+0x638/0xa7c net/bpf/test_run.c:594
   bpf_prog_test_run kernel/bpf/syscall.c:3148 [inline]
   __do_sys_bpf kernel/bpf/syscall.c:4441 [inline]
   __se_sys_bpf+0xad0/0x1634 kernel/bpf/syscall.c:4381

  kfence-#213: 0xffff6254fffac000-0xffff6254fffac196, size=407, cache=kmalloc-512

  allocated by task 15074 on cpu 0 at 1342.585390s:
   kmalloc include/linux/slab.h:568 [inline]
   kzalloc include/linux/slab.h:675 [inline]
   bpf_test_init.isra.0+0xac/0x290 net/bpf/test_run.c:191
   bpf_prog_test_run_skb+0x11c/0xa7c net/bpf/test_run.c:512
   bpf_prog_test_run kernel/bpf/syscall.c:3148 [inline]
   __do_sys_bpf kernel/bpf/syscall.c:4441 [inline]
   __se_sys_bpf+0xad0/0x1634 kernel/bpf/syscall.c:4381
   __arm64_sys_bpf+0x50/0x60 kernel/bpf/syscall.c:4381

To fix the problem, we adjust @size so that (@size + @hearoom) is a
multiple of SMP_CACHE_BYTES. So we make sure the struct skb_shared_info
is aligned to a cache line.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2022-49840?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2022-49840?

Apply the vendor's patch.

## Is CVE-2022-49840 being exploited?

There is no known exploitation of CVE-2022-49840 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-2022-49840 and fix it if it is affected.

What it is: CVE-2022-49840 is a high-severity use after free vulnerability in Linux kernel, published on 1 May 2025. 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-2022-49840 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-2022-49840/ (Markdown: https://insights.sbomify.com/CVE-2022-49840/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2022-49840
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2022-49840
- OSV: https://osv.dev/vulnerability/CVE-2022-49840

---
From sbomify Insights: https://insights.sbomify.com/CVE-2022-49840/
Summaries are generated and may contain mistakes; the official description above is the record.