# CVE-2021-47014: net/sched: act_ct: fix wild memory access when clearing fragments

> A wild memory access in the Linux kernel's net/sched act_ct module can cause a system crash when clearing IP fragments.

- **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:** 28 Feb 2024
- **Updated:** 5 Aug 2026
- **Also known as:** DEBIAN-CVE-2021-47014, GHSA-94mv-98xv-9mqq, ROOT-OS-DEBIAN-11-CVE-2021-47014, UBUNTU-CVE-2021-47014

## What is CVE-2021-47014?

CVE-2021-47014 is a high-severity memory corruption vulnerability in Linux kernel, published on 28 Feb 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:

net/sched: act_ct: fix wild memory access when clearing fragments

while testing re-assembly/re-fragmentation using act_ct, it's possible to
observe a crash like the following one:

 KASAN: maybe wild-memory-access in range [0x0001000000000448-0x000100000000044f]
 CPU: 50 PID: 0 Comm: swapper/50 Tainted: G S                5.12.0-rc7+ #424
 Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.4.3 01/17/2017
 RIP: 0010:inet_frag_rbtree_purge+0x50/0xc0
 Code: 00 fc ff df 48 89 c3 31 ed 48 89 df e8 a9 7a 38 ff 4c 89 fe 48 89 df 49 89 c6 e8 5b 3a 38 ff 48 8d 7b 40 48 89 f8 48 c1 e8 03 <42> 80 3c 20 00 75 59 48 8d bb d0 00 00 00 4c 8b 6b 40 48 89 f8 48
 RSP: 0018:ffff888c31449db8 EFLAGS: 00010203
 RAX: 0000200000000089 RBX: 000100000000040e RCX: ffffffff989eb960
 RDX: 0000000000000140 RSI: ffffffff97cfb977 RDI: 000100000000044e
 RBP: 0000000000000900 R08: 0000000000000000 R09: ffffed1186289350
 R10: 0000000000000003 R11: ffffed1186289350 R12: dffffc0000000000
 R13: 000100000000040e R14: 0000000000000000 R15: ffff888155e02160
 FS:  0000000000000000(0000) GS:ffff888c31440000(0000) knlGS:0000000000000000
 CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
 CR2: 00005600cb70a5b8 CR3: 0000000a2c014005 CR4: 00000000003706e0
 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
 Call Trace:
  <IRQ>
  inet_frag_destroy+0xa9/0x150
  call_timer_fn+0x2d/0x180
  run_timer_softirq+0x4fe/0xe70
  __do_softirq+0x197/0x5a0
  irq_exit_rcu+0x1de/0x200
  sysvec_apic_timer_interrupt+0x6b/0x80
  </IRQ>

when act_ct temporarily stores an IP fragment, restoring the skb qdisc cb
results in putting random data in FRAG_CB(), and this causes those "wild"
memory accesses later, when the rbtree is purged. Never overwrite the skb
cb in case tcf_ct_handle_fragments() returns -EINPROGRESS.

Weakness: CWE-754 (Improper Check for Unusual or Exceptional Conditions)

## Which versions are affected by CVE-2021-47014?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2021-47014?

Apply the vendor's patch.

## Is CVE-2021-47014 being exploited?

There is no known exploitation of CVE-2021-47014 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-2021-47014 and fix it if it is affected.

What it is: CVE-2021-47014 is a high-severity memory corruption vulnerability in Linux kernel, published on 28 Feb 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-2021-47014 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-2021-47014/ (Markdown: https://insights.sbomify.com/CVE-2021-47014/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-47014
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-47014
- OSV: https://osv.dev/vulnerability/CVE-2021-47014

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-47014/
Summaries are generated and may contain mistakes; the official description above is the record.